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Annals of the ICRPICRP PUBLICATION XXX

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Radiological Protection in PET and PET/CT

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Editor-in-Chief

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C.H. CLEMENT

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Associate Editor

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T. YASUMUNE
Authors on behalf of ICRP
J.M. Martí-Climent, S. Demeter, S. Holm, M. Hosono, K. Kang,
M. Marengo, C. J. Martin, D. Newman, A.I. Santos, F. Vanhavere

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PUBLISHED FOR

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The International Commission on Radiological Protection

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by

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Please cite this issue as ‘ICRP, 20YY. Radiological Protection in PET and PET/CT.
ICRP Publication XXX, Ann. ICRP xx (x).’361DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE
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CONTENTS

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ABSTRACT.................................................................................................................................. 539

MAIN POINTS ............................................................................................................................. 7

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EXECUTIVE SUMMARY .......................................................................................................... 8411.

1.1. Nuclear medicine and PET.............................................................................................. 11
1.2. Radiological protection in medicine ............................................................................... 121.3. Coverage of PET and PET/CT in previous ICRP Publications ...................................... 13
1.4. Frequency of PET examinations and patient exposure ................................................... 14
1.5. Public exposure ............................................................................................................... 15
1.6. Staff exposure.................................................................................................................. 16
1.7. Education and ongoing training ...................................................................................... 16
1.8. Scope ............................................................................................................................... 16
1.9. Target audience ............................................................................................................... 17

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IMAGING EQUIPMENT LIFE CYCLE ........................................................................... 55
4.1. The life cycle of equipment............................................................................................. 55
4.2. Acquisition of equipment ................................................................................................ 56
4.3. Enabling and installation of equipment........................................................................... 58
4.4. Operational requirements for equipment in clinical use ................................................. 59
4.5. The end of clinical use and equipment disposal.............................................................. 60

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PET/CT FACILITY DESIGN ............................................................................................ 32
3.1. Types of PET/CT facility ................................................................................................ 32
3.2. Cyclotron facilities .......................................................................................................... 33
3.3. PET radiopharmacy/radiochemistry laboratory .............................................................. 38
3.4. Radiation components of PET/CT imaging .................................................................... 41
3.5. The journey of the PET patient through the facility ....................................................... 42
3.6. Design of a PET facility .................................................................................................. 46
3.7. Determination of shielding requirements for a PET/CT imaging facility ...................... 51

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PET AND PET/CT PRINCIPLES ...................................................................................... 18
2.1. PET, principles and technology ...................................................................................... 18
2.2. CT technology ................................................................................................................. 23
2.3. PET/CT ........................................................................................................................... 25
2.4. PET/MR .......................................................................................................................... 26
2.5. Cyclotron ......................................................................................................................... 27
2.6. Clinical applications and radiopharmaceuticals .............................................................. 30

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INTRODUCTION .............................................................................................................. 11

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JUSTIFICATION AND OPTIMISATION OF PET, PET/CT AND PET/MRI ................ 622

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5.1. Characteristics of PET, PET/CT, and PET/MRI in association with justification.......... 62
5.2. Justification of radiological practices.............................................................................. 63
5.3. Justification of PET, PET/CT, and PET/MRI procedures .............................................. 63
5.4. Optimisation of radiological practices ............................................................................ 65

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6. OPTIMISATION RELATED TO THE MEDICAL EXPOSURE OF PATIENTS,
CARERS/COMFORTERS, AND RESEARCH VOLUNTEERS ............................................. 67

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6.1. Dose estimation of patients ............................................................................................. 67
6.2. Optimisation and dose reduction strategies .................................................................... 70
6.3. Radiological protection optimisation using both hardware and software ....................... 71
6.4. The value of DRLs for optimisation of PET and PET/CT .............................................. 72
6.5. Radiological protection and dose issues in paediatric patients ....................................... 76
6.6. Breast Feeding................................................................................................................. 78
6.7. Fetal dose ........................................................................................................................ 78
6.8. Carers/Comforters ........................................................................................................... 79
6.9. Research volunteers ........................................................................................................ 80

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7.1. Background ..................................................................................................................... 82
7.2. General recommendation on radiation dose to the general public .................................. 83
7.3. Radiation dose to non-radiation workers ........................................................................ 83
7.4. Patient to patient dose ..................................................................................................... 84

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OPTIMISATION FOR STAFF .......................................................................................... 85
8.1. Sources ............................................................................................................................ 85
8.2. Measures to optimise staff radiological protection ......................................................... 99
8.3. Staff dose monitoring .................................................................................................... 109

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RADIOLOGICAL PROTECTION FOR THE PUBLIC .................................................... 82

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DOSE MANAGEMENT AND QUALITY ASSURANCE PROGRAM ........................ 115

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9.1. Regulatory authority and legal framework ................................................................... 115
9.2. Optimisation of dose to patient ..................................................................................... 117
9.3. Optimisation of equipment parameters ......................................................................... 119
9.4. QA/QC program overview in a PET imaging facility .................................................. 120
9.5. Components of QC program ......................................................................................... 122
9.6. QC Testing PET, PET/CT, or PET/MRI....................................................................... 123
9.7. QC testing radionuclide calibrator ................................................................................ 127
9.8. QC radiation monitoring instruments and other equipment.......................................... 127
9.9. Summary overall QC program ...................................................................................... 128

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10. EDUCATION AND TRAINING IN RADIOLOGICAL PROTECTION ....................... 129

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10.1. Foreword ..................................................................................................................... 129
10.2. International stakeholders’ recommendations ............................................................ 129
10.3. Main responsibilities regarding education and training.............................................. 132
10.4. Health care professional training in radiological protection and safety ..................... 134
10.5. Formal and informal educational training priorities and certification in PET/CT ..... 136
10.6. Continuous professional development (CPD) and self-assessment needs ................. 139

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10.7. Final remarks .............................................................................................................. 142

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REFERENCES ......................................................................................................................... 143

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ACKNOWLEDGEMENTS ...................................................................................................... 160

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RADIOLOGICAL PROTECTION IN PET AND PET/CT

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ICRP PUBLICATION XXX

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Approved by the Commission in MMMM 20YY

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Abstract–Positron Emission Tomography (PET) is a nuclear medicine imaging procedureused today almost exclusively in multimodal imaging particularly with computed tomography(CT) but also with magnetic resonance (MR), rather than alone. Its utilisation rates are
growing as clinical indications expand with the addition of new PET radiopharmaceuticals. In
some countries, PET/CT scans currently make up about 10% of all nuclear medicine
examinations and about 20% of the patient effective dose delivered in nuclear medicine.
Radiation doses depend not only on the administered activity, but also on the CT scanutilisation. Shorter half-lives of PET radionuclides and the high energies of annihilation
photons emitted present particular challenges for staff radiological protection, which arecompounded because patients are required to rest for an extended period between
administration and imaging. Occupational doses in PET can be of few mSv per year, and skindoses to the fingers from manipulating PET radiopharmaceuticals can exceed the annual skindose limit of 500 mSv if proper protection measures are not followed. Public exposure is nota cause for concern, and no special recommendations are needed to limit the release of thepatient after the PET scan. However, patients and clinicians remain concerned and therefore,
this report provides guidance on not only occupational, but also patient, and public
radiological protection in PET and PET/CT. A brief section on PET/MR is also provided.
The technology involved and the way in which it is used together with the facility design has
a direct impact on patient and staff dose. Consequently, the principles of operation of both thecyclotron used for production of the radionuclides and of the scanner are reviewed in thisreport; the report describes optimal facility design, equipment life cycle considerations, andwork flow for the radiopharmaceutical agents.
The justification of the PET procedure should be established considering also the technology
available, and when performed in a PET/CT scanner, the CT protocol should correspond tothe objective of the CT examination. Distinct considerations are provided for the radiologicalprotection related to the medical exposure of patients, carers/comforters, and research
volunteers, including patient dose estimation, strategies to reduce the dose, and the special
cases of patients who are breast feeding or pregnant, and paediatric patients.
Sources of exposure to staff working in PET facilities have been reviewed, and records showthat dose depends not only on the protective methods but also on the individual practices,education, and quality assurance program. Therefore, procedures to reduce staff dose areprovided together with guidance for staff monitoring. Optimisation of radiological protection
for PET should be within the frame of a dose management and quality assurance program,which describes the radiological protection program and includes metrics to evaluate the
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degree of achievement. In addition, the health professionals that perform the procedures mustobtain proficiency in radiological protection and safety through formal, accredited education,
training, and continuous professional development.
© 20YY ICRP. Published by SAGE.
Keywords: PET; PET/CT; PET/MR; Radiological protection; Patient; Staff; Public

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MAIN POINTS

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Planning of positron emission tomography (PET) facilities is crucial for theradiological protection of the patient, staff, and public. Proper shielding andmaximum automation of the radiopharmaceutical handling should be employed andthe rooms within a PET department should be arranged to facilitate patient
movement, while minimising the exposure of staff members and other patients.

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The justification of PET, PET/CT, and PET/MR should involve consideration of thecharacteristics of the imaging technologies, and take account both of the PET
radiopharmaceutical and the choice of protocol to achieve the clinical objective of theCT examination, with special consideration given to paediatric patients. Imaging
protocols should be optimised for the clinical task, and national diagnostic reference
levels (DRLs) should be established for both the PET and CT components.

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Occupational doses in PET can be close to one-third of the dose limit, and skin doses
to the fingers from manipulating PET radiopharmaceuticals can exceed the annual
skin dose limit, if proper protection measures are not followed. Adoption of
appropriate shielding devices is important, but the individual techniques andoptimisation of working practices are crucial.

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Whole-body monitoring should be carried out based on monthly measurements, andHp(10) measurement from a dosimeter worn on the upper body will also provide anapproximate indication of dose to the eye lens. Monitoring extremity doses with
fingertip or ring dosimeters is recommended, with correction factors to estimate themaximum dose over the two hands.

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Appropriate standards should address radiological protection in a PET facility forpatients, staff, and public. Each member of the medical imaging team has a crucial
and defined role and must obtain proficiency in radiological protection throughformal education, training, and continuous professional development. The teammembers should work together to ensure that the agreed goals and objectives of thequality assurance program are being met.

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EXECUTIVE SUMMARY

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(a) Positron emission tomography (PET) is a nuclear medicine diagnostic techniqueproviding functional, metabolic, and molecular information by means of positron emitters.
The positron emitted undergoes annihilation producing two 511 keV photons that can bedetected by the PET scanner. This can be used together with computed tomography (CT) in a
PET/CT scanner, or with magnetic resonance imaging (MRI) in a combined PET/MR;
providing better anatomical detail (hybrid fused images). The utilisation rates of PET are
growing as clinical indications expand with the addition of new PET radiopharmaceuticals. In
some countries, PET/CT scans currently make up about 10 % of all nuclear medicine
examinations and about 20 % of the effective dose delivered in nuclear medicine. The shorthalf-lives of PET radionuclides and the high energies of annihilation photons emitted present
challenges for radiological protection of staff. This publication provides guidance on
occupational, patient, and public radiological protection in PET and PET/CT.
(b) Medical diagnosis using PET hybrid imaging requires knowledge of the technology,
anatomy and physiology, and disease states involved, as well as the possible alternative
imaging options in order to achieve optimisation of radiological protection. Patient
preparation, the performance of the PET/CT scanner and the parameters employed during theimage acquisition and reconstruction, have an impact on both the image quality and dose
received by the patient. New PET equipment with improved resolution, extended field ofview and increased sensitivity, together with extended acquisition modalities and improved
reconstruction techniques, can effectively reduce image noise without increasing
administered activity to the patient. CT parameters have an impact on the image quality andpatient dose. Imaging with CT or MRI are be used with PET although each has pros andcons: for example, the type of anatomical information provided is different, thecontraindications for MR in some patients with implants but the benefit of avoiding ionisingradiation when using MR. The short half-life of PET radionuclides requires either an on-site
cyclotron or a fast distribution system. In addition, generator systems can be used for
production of other PET radionuclides. All production systems require specific radiologicalprotection for the staff.
(c) The planning and layout of the PET facility has a direct impact on radiologicalprotection for patients, staff, and the public. Cyclotron vaults, radionuclide transfer systems
and laboratory facilities should be designed to protect against irradiation and contamination,and the release of the radioactive gases. Arrangements should be in place for monitoringgaseous releases. Adequate shielding and automation when manipulating theradiopharmaceuticals during synthesis, filling vials, dispensing and administration should beconsidered when setting up the facility. The layout of the imaging part of the facility shouldbe planned taking account of movement of the patient, including the resting period in a bay,
between the radiopharmaceutical administration and the imaging procedure; in order tominimise the exposure of staff members and other patients. The dominant protection will beagainst 511 keV gamma-ray photons, although CT x-ray photons must be considered in the
PET/CT scanning room. It is important to consider the life cycle of the PET equipment andfacility. The stages in the planning and creation of a PET facility include justification,
specification, acquisition, installation, acceptance, commissioning, and user training, before
the system is put into clinical use. The disposal of the equipment and of the sealed sources
used in the facility to verify and calibrate the PET scanner will need to be considered towards
the end of the clinical use.

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DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE(d) The justification of radiological practices is at three levels of application. At the firstlevel, the proper use of radiation in medicine is accepted, at the second level, a considerable
amount of evidence has been accumulated on the role and potential applications of a specifictechnology in the management of patients in a variety of conditions and affected by different
pathologies. The application of a PET procedure to each individual patient should bejustified, which involves justification at the third level. Patient dosimetric considerations
should be part of justification as well as optimisation, including the choice of theradiopharmaceutical and of the modalities of acquisition and image reconstruction for boththe components, PET and CT, of a multimodality imaging system. The CT component of themultimodality scan may have several different objectives, i.e. attenuation/scatter correction,
low dose anatomic localisation or diagnostic image interpretation which will require a higher
dose level, and this leads to a broad range of radiation doses to patients. The appropriate
protocol should be selected to fulfil the purpose.
(e) In a PET/CT examination, the total radiation dose is a combination of the dose fromthe PET radiopharmaceutical and that from the CT. The dose received by the patient isdirectly proportional to the activity of the radiopharmaceutical administered to the patient.
National diagnostic reference levels (DRL) should be established for both the PET and CT
components to aid optimisation. New PET, PET/CT, or PET/MRI hardware and software canreduce radiation dose while maintaining image quality. For paediatric patients, justificationand optimisation in both PET and CT components have special considerations. Infants thatare breastfed by mothers who have been submitted to a PET exam have two potential sourcesof radiation, the radiopharmaceutical itself which can be excreted in breast milk, and external
exposure during the act of breastfeeding. Radiological protection principles should also be
applied for carers and comforters of the patient.
(f) Patients undergoing diagnostic PET radiopharmaceutical studies generally do not posea significant radiation risk to the public. No specific post imaging restrictive advice isrecommended; 'holding' the patient post imaging in a separate waiting area to allow forfurther dose rate reduction post imaging is not necessary and is not recommended. The
general advice is not to bring accompanying persons especially children, and by extension
pregnant women, to the facility. Radiological protection measures such as administeredactivity, distance, time, shielding, facility design, and restricted access need to be considered
to protect other patients, non-radiation workers, and the general public during the PET
radiopharmaceutical uptake period and during PET/CT imaging.
(g) Occupational doses in PET can be of few mSv per year, and skin doses to the fingers
from manipulating PET radiopharmaceuticals can exceed the annual skin dose limit of 500
mSv if proper protection measures are not followed. As shown in the document, dose
depends not only on the protective methods but also on individual practices. Therefore,
optimisation of the working practices is crucial. Patient preparation and co-operation areimportant factors in minimising contact time and in increasing the distance between patientand staff member, and so the dose directly from the patient. The optimisation of the working
practice and the application of shielding for the vial and syringe are important factors in
reducing the magnitude of doses to the fingers when radiopharmaceuticals are handled.
(h) Whole-body doses to the staff should be monitored based on monthly measurements,
and the measurement from a dosimeter worn on the upper body will also provide anapproximate indication of dose to the eye lens. The most exposed area of the hand is often the
tip of the index finger of the non-dominant hand, but this does vary, so individual monitoring
to establish dose patterns is important. It is recommended to monitor extremity doses witheither fingertip dosimeters or ring dosimeters, with correction factors to estimate themaximum dose over the two hands.

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DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE(i) The Quality Assurance and Quality Control program in PET or PET/CT must addressand ensure radiological protection and safety related to medical, occupational and public
exposures. Each member of the medical imaging team has a crucial and defined role. The
quality assurance program must include metrics to demonstrate that the goals and objectivesof the program are being met. In addition, each facility should have a system for reporting
and reviewing undesired events (accidents, misadministration, near misses).
(j) Education and training in radiological protection is a key issue. International
stakeholders have detailed the responsibilities and needs for education and training inRadiological Protection for all groups of health professionals involved in a PET or PET/CT
facility. The health professional performing the procedures in the facility must obtainproficiency in radiological protection and safety through formal education, training andcontinuous professional development. These educational programmes could be establishedbased on educational documents and tools developed by stakeholders and some Scientific
Societies and Councils.

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1. INTRODUCTION

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1.1. Nuclear medicine and PET

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(1) Nuclear medicine is a medical speciality that involves the use of radiopharmaceuticals
in the diagnosis and treatment of patients. In diagnostic procedures, short-lived radionuclides
that label an appropriate pharmaceutical are used to examine organ function and thereby
diagnose disease. The images obtained give functional, metabolic, and molecular
information. Gamma or annihilation photons produced as a consequence of radioactive
disintegration are detected with a suitable system and this information is presented in images
that show the biodistribution of the radiopharmaceutical. Traditionally, the radionuclides
used in diagnostic nuclear medicine have been radionuclides that emit gamma photons.
(2) Positron emission tomography (PET) is a nuclear medicine technique that produces
images of the distribution within the body of radioactive tracers that emit positrons, such as
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C, 13N, 15O, and 18F. The positron emitted during disintegration undergoes annihilation with
an electron, producing two photons that can be detected by the PET scanner. PET
radiopharmaceuticals can be incorporated readily into biological processes and have an
increasingly important role in oncology, namely in diagnosis, staging, treatment response andassessment for recurrence. They are also used in neurology and cardiology. PET is used
together with computed tomography (CT) in a PET/CT scanner to provide better anatomical
detail (hybrid fused images), and thus increase specificity and diagnostic accuracy. CT
images are used to correct for the attenuation of the annihilation photons in the patient's body.
Introduced in early 2000 (Beyer et al., 2002), PET/CT scanners have become the standard
technology configuration for PET imaging. The integration of positron emission tomography
and magnetic resonance imaging (MRI) in a combined PET/MR scanner provides anotherbimodal approach with functional-anatomical and multiparametric applications (Herzog and
Van Den Hoff, 2012).
(3) A few positron emitting radionuclides are produced by generators, such as 68Ge/68Ga,
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Zn/62Cu, and 82Sr/82Rb. Most PET radiopharmaceuticals, however, are labelled with 11C,
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N, 15O, or 18F, which are produced in a cyclotron. Due to their short half-lives (from 2
minutes to a little under 2 hours), there are some limitations to their distribution, and some
PET/CT facilities have their own cyclotron and a laboratory to label PET tracers.
(4) The directory of cyclotrons used for radionuclide production in 39 Member States of
the IAEA, updated in 2006, had 262 entries for cyclotrons. This was an increase of 7% overthe 246 reported in the 2002 cyclotron directory. However, it was believed to be a total of
about 350 cyclotrons operating in the world, involved in some aspects of radionuclide
production. The increase in number during these years was driven by several factors:
advances in medical imaging, the introduction of a compact, user friendly medical cyclotron;
and a decision that costs for [15O]-oxygen PET studies in Japan and 2-[18F]FDG PET studies
in Germany and the United States of America were eligible for reimbursement bygovernment or health insurance companies. 75 % of the cyclotrons were used to produce 2[18F]FDG, either for in-house use or for distribution to external facilities, and 36% of thecentres producing 2-[18F]FDG were distributing it (IAEA, 2006). The number of cyclotrons isstill increasing, with more than 1300 cyclotron facilities worldwide (IAEA, 2021a), and 1484
are quoted in by another report (Goethals, 2020). Since this data depends on voluntary datacollection, the number of cyclotrons could be higher and is estimated at around 2000.
(5) The use of unsealed radionuclides, which implies their production, and the use of CT
in diagnostic PET examinations, involves exposure of staff, patients and public to two
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different radiation sources. Exposure must be optimised, and for the patient also withoutcompromising their diagnosis, by means of appropriate design of the facility and by means ofgood working and administrative procedures.
(6) This report will cover the principles and technology behind PET and PET/CT, andinclude a summary of the clinical applications in Section 2, provide general guidelines on
facility design in Section 3, and review the imaging equipment life cycle in Section 4.
(7) Categories of medical and healthcare professionals working in PET, and therefore in
PET/CT or PET/MR, considered in this report are nuclear medicine specialists, radiologists
specialists, radiopharmacists, and radionuclide laboratory staff, nursing staff and other
healthcare professionals assisting in radiopharmaceutical administration, nuclear medicine
technologists/radiographers, medical physicists, maintenance engineers, and clinicalapplications specialists, with duties described in Publication 113 on 'Education and Training
in Radiological Protection for Diagnostic and Interventional Procedures' (ICRP, 2009).
Where there are citations to data in the literature, the category names of the professionals in
the references used have not been changed.

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1.2. Radiological protection in medicine

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(8) The primary aim of radiological protection is to provide an appropriate standard ofprotection for people and the environment without unduly limiting the beneficial practices
giving rise to radiation exposure. Publication 103 untitled The 2007 'Recommendations of
the International Commission on Radiological Protection' (ICRP, 2007b) sets the threefundamental principles of radiological protection, namely justification, optimisation, and theapplication of dose limits.
(9) Two principles are source-related and apply in all exposure situations:• The principle of justification: Any decision that alters the radiation exposure situation
should do more good than harm
• The principle of optimisation of protection: the likelihood of incurring exposures, thenumber of people exposed, and the magnitude of their individual doses should all be
kept as low as reasonably achievable, taking into account economic and societal
factors.

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And one principle is individual-related and applies in planned exposure situations:• The principle of application of dose limits: The total dose to any individual from
regulated sources in planned exposure situations other than medical exposure ofpatients should not exceed the appropriate limits recommended by the Commission.

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These three principles apply to the radiological protection of the worker and the public.
(10) In relation to occupational exposure and practical protection methods, the principles
of how to protect workers from ionising radiation, including those in the field of medicine,are discussed fully in Publication 75 on 'General principles for the radiation protection ofworkers' (ICRP, 1997a); these principles apply to staff in PET/CT facilities. The control ofoccupational exposure is of particular importance during radiopharmaceutical preparation bystaff in nuclear medicine, and careful shielding and time limits are needed (ICRP, 2007a).
(11) Publication 105 on 'Radiation Protection in Medicine' (ICRP, 2007a) was prepared tounderpin the Commission’s 2007 Recommendations (ICRP, 2007b) with regard to the
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biomedical research. It addresses the proper application of the fundamental principles(justification, optimisation of protection, and application of dose limits) of the Commission’s
2007 Recommendations with respect to the above-mentioned groups of individuals.
(12) For patients, there are three levels of justification for use of radiation: at the first level,
the proper use of radiation in medicine is accepted as doing more good than harm to society;at the second level, a procedure with a specified objective is defined and justified; and at thethird level, the application of the procedure to an individual patient should be justified. The
optimisation of radiological protection in medicine is usually applied at two levels: thedesign, appropriate selection, and construction of equipment and installations; and the day-today methods of working (i.e. the working procedures) (ICRP 2007a).
(13) The principle of optimisation has been a major part of radiological protection thinking
for three decades (ICRP, 1991) and is key to effective use of medical imaging. Optimisationin relation to medical imaging requires provision of clinical images for individual patientsthat are of sufficient quality to ensure accurate and reliable diagnoses, in order to enable
informed care decisions to be made. In addition, the radiation doses used in acquiring suchclinical images should be adjusted so that, while being adequate to produce the images, they
are minimised to the level appropriate to the applied imaging technology (ICRP, year2).
(14) The optimisation of radiological protection for patients in medicine is usuallyapplied at two levels: (1) the design, appropriate selection, and construction of equipment andinstallations; and (2) the day-to-day working procedures. The basic aim of this optimisationof protection is to adjust the protection measures for a source of radiation in such a way thatthe net benefit is maximised. The optimisation of radiological protection is best described as
management of the radiation dose to the patient to be commensurate with the medical
purpose. Therefore, it is not appropriate to apply dose limits or dose constraints, because such
limits may often do more harm than good (ICRP, 2007a).
(15) Optimisation is not a single action and there are many aspects that need to be in place
before a PET or PET/CT facility can even embark on the road to achieving optimisation;these are not straight forward and have become quite complex in the healthcare environment.
Proper initial education and ongoing training of staff on operation of equipment is crucial tostarting the process (Vassileva et al., 2022). However, this needs to be coupled witharrangements for the ongoing monitoring, review, and analysis of imaging performance, thatcan be used to gradually improve overall effectiveness (ICRP, year1). Optimisation of
medical imaging requires continuing development of knowledge, skills, competencies, andexperience of all professionals involved in the imaging process (ICRP, year2).
(16) As dose limits are not used with patients, Diagnostic Reference Levels (DRLs) areapplied for a particular procedure and used as an optimisation tool (ICRP 2007a). DRLs wereintroduced by the Commission in Publication 73 on ' Radiological protection and safety inmedicine' (ICRP, 1996), and developed further in a Supporting Guidance (ICRP, 2001) andin Publication 135 on 'Diagnostic reference levels in medical imaging' (ICRP, 2017a). In
diagnostic nuclear medicine, administered activity [in becquerels (Bq)], or, preferably,administered activity per body weight, is the measurable quantity used to indicate themagnitude of a patient's internal irradiation. This quantity is used to assist in managing thepatient dose. For PET/CT, as a system that combines two imaging modalities, DRL values
should be set for each modality independently (ICRP, 2017a).

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1.3. Coverage of PET and PET/CT in previous ICRP Publications

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(17) Publication 84 entitled 'Pregnancy and medical radiation' provides clarification onrisks to the embryo and fetus from medical exposure (ICRP, 2000). It also offers general
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advice for diagnostic nuclear medicine procedures, focusing on gamma emitters, covering
scenarios before, during, and after a diagnostic procedure as well as the breast-feeding
scenario.
(18) Publication 95 on 'Doses to infants from radionuclides ingested in mothers’ milk'reported information on radiation doses to infants due to intake of radionuclides in maternal
milk. (ICRP, 2004). Dose coefficients per unit intake by the mother were given for selectedradionuclides of 35 elements that could be released into the environment due to various
human activities. These radionuclides included the 99mTc used in nuclear medicine but not
PET radionuclides.
(19) Publication 128 on 'Radiation dose to patients from radiopharmaceuticals: acompendium of current information related to frequently used substances' (ICRP, 2015a)
provided a compendium of current information relating to radiation dose to patients fromradiopharmaceuticals. The information includes biokinetic models, biokinetic data, dosecoefficients for organ and tissue absorbed doses, and effective dose for the major nuclear
medicine diagnostic radiopharmaceuticals. The radiation dose calculations are based on theradiological protection guidance given in Publication 60 (ICRP, 1991) and cover 19 PET
radiopharmaceuticals. These data were mainly compiled from Publications 53, 80, and 106(ICRP, 1987, 1998, 2008a), and related amendments and corrections. Diagnostic procedureswith positron emitting radiopharmaceuticals were included in the recommendations.
Publication 106 (ICRP, 2008a) also included annexes on 'Recommendations on breastfeeding interruptions' (Annex D), and on 'Radiation exposure of hands in radiopharmacies:
monitoring of doses and optimisation of protection' (Annex E). With regard to breast-feeding,if correct procedure is followed, a baby should not be breast fed until the radiopharmaceuticalis no longer secreted in an amount estimated to give an effective dose of >1 mSv. With
regard to hand exposure, the report was mainly focused on 99mTc as it was the most common
radionuclide used in nuclear medicine, and at that time there was also limited information on
hand exposure to PET radiopharmaceuticals.
(20) Training requirements and suggested content for training courses in nuclear medicine,including the radiological protection for personnel working in PET/CT, was included in the
Publication 113 on 'Education and training in radiological protection for diagnostic andinterventional procedures' (ICRP, 2009) considering the categories of medical and healthcare
professionals specified in section 1.1.
(21) Finally, in Publication 139 on 'Occupational radiological protection in interventional
procedures' (ICRP, 2018), PET/CT was considered when used for radiological imaging to
guide interventional procedures. In this context, the principal factor determining radiation
exposure to the operator was the time spent in close proximity to the patient.

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(22) The annual frequency of diagnostic nuclear medicine examinations per 1000 people indeveloped countries increased from 16 in 1985–1990 to 19 in 1997–2007 (UNSCEAR,
2010). In European countries only, the annual frequency was somewhat lower: 14 per 1000 in
the period 2007–2010 (EC, 2014a). The increasing relevance of PET and PET/CT isdemonstrated by the fact that the UNSCEAR 2008 report included these examinations per
million of population for different countries (UNSCEAR, 2010), while these data were notincluded in the previous report (UNSCEAR, 2000).
(23) The average frequency per 1000 of population of the five most-common nuclear
medicine diagnostic procedures was 13.7 for UNSCEAR health-care level 1 countries (in1997–2007, level based on the number of physicians per population), and 9.2 for European
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countries (in 2007–2010). For PET and PET/CT the frequencies were 0.9 for UNSCEAR
health-care level 1 countries and 0.8 for European countries (EC, 2014a).
(24) The annual per person effective dose due to diagnostic nuclear medicine examinationsin health-care level 1 countries was estimated to be 0.08 mSv for the period 1990–1996(UNSCEAR, 2000). The estimate was 0.12 mSv for the period 1997–2007 (UNSCEAR,
2010). At the time, doses due to PET studies were estimated to be at the high end of thespectrum for diagnostic nuclear medicine procedures; and the 511 keV annihilation photons
contributed to staff radiation doses. PET procedures accounted for an average of 18% of
nuclear medicine procedures. The average change in frequency of nuclear medicine
procedures since the UNSCEAR 2008 Report was +14% (UNSCEAR, 2022).
(25) By the year 2000, the development of new compounds for labelling with short-lived
positron-emitting radionuclides was enabling a broad range of metabolic tracer imaging andphysiological studies through the use of PET (UNSCEAR, 2000). Over 1000 compounds had
been labelled to study specific biochemical processes and physiologic function by PET;
however clinical applications in oncology, cardiology and neurology relied upon 25 different
PET radiopharmaceuticals, although for their specific clinical needs, most PET centres use 2
to 5 PET radiopharmaceuticals (Lambrecht, 1998).
(26) In Europe, data from national surveys carried out between 2007 and 2010 showed thatwhile PET and PET/CT constituted about 6 % of nuclear medicine diagnostic procedures, themedian contribution of tumour imaging with PET and PET/CT to the total per caput effective
dose was about 16 %. Of all nuclear medicine procedures, PET together with PET/CT was
identified as having the fourth highest contribution to the total effective dose (EC, 2014a). In
England, the number of PET/CT scans increased by 16.2% between 2016/17 and 2017/18(NHS, 2018). In USA, tumour imaging with PET represented 14.6 % of the nuclear medicine
studies in 2016 and was the second largest contributor to the dose from nuclear medicine
studies (NCRP, 2019). Worldwide, 2-[18F]FDG is the most used PET radiopharmaceutical.
The utilisation of PET/CT imaging is increasing, and indications in oncology, inflammation,
cardiology and neurology are expanding with the addition of new PET radiopharmaceuticals.
(27) Patient exposure from PET/CT examinations depends not only on the administeredactivity, but also on the nature of the CT scan. The degree of exposure is expected to depend
on whether CT is used for anatomical localisation and attenuation correction or to provide thenecessary image quality for diagnosis, with or without intravenous (i.v.) iodine contrast
agent, resulting in a higher CT dose.
(28) PET and PET/CT justification is reviewed in Section 5, while the radiologicalprotection related to the medical exposure of patients, carers and comforters, and research
volunteers is considered in Section 6, as well as the exposure of infants breast fed fromwomen who have had a recent PET radiopharmaceutical injection, and fetus exposure.
Patient dose management and development of a quality assurance program when working
with PET/CT will be covered in Section 9.

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1.5. Public exposure

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(29) Public radiation exposure includes exposure to members of the general public,
workers who are not designated as nuclear or radiation workers, and unintended patient-topatient exposure after PET radiopharmaceutical administration. In a well-designed facility,
public exposure should not be a cause for concern. Because the half-life of most positron
emitter radionuclides is short, irradiation of the public by patients is usually lower than thatwith other nuclear medicine examinations. Recommendations concerning minimization of
public exposure will be provided in Section7.
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1.6. Staff exposure

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(30) The short half-lives of PET radionuclides and the high energies of annihilation
photons emitted (i.e. 511 keV) present particular challenges for staff radiological protection.
These challenges are compounded by the fact that patients are required to rest for an extended
period between PET radiopharmaceutical administration and imaging. While the worldwide
average annual effective dose for monitored workers in nuclear medicine was 0.7 mSv(2000–2002), the annual doses for PET technologists were higher than those for technologists
performing general nuclear medicine studies, with values averaging about 3 mSv and 2 mSv,
respectively, and occupational exposure could be higher for technologists than for physiciansworking in PET by a factor of 2–4 (UNSCEAR, 2010). Large variations in staff doses arereported between centres, however when the PET centre is appropriately designed andpersonnel are well trained, a highly productive operation centre can be achieved with wholebody doses to staff not exceeding 5 mSv per year (IAEA, 2008a). These dose differences
depend on the degree of optimisation of facility shielding and design, the protection tools
available, the techniques used by staff, number of patients, and the level of experience andinvolvement of the staff in implementing protection methods.
(31) The ORAMED project (7th EU Framework Programme, 2008–2011), which
evaluated dose distribution across the hands while preparing and administering 18F- and99m
Tc-labelled radiopharmaceuticals, showed that the preparation of 18F was the most criticalof the studied diagnostic procedures (Vanhavere et al., 2012); the fraction of workers whowent over the annual equivalent dose limit for the extremities of 500 mSv was estimated tobe 23% and 40% for 18F administration and preparation, respectively, showing the need forproper protection measures. In the study, several participating centres did not use shieldedvials and syringe, and before 2010 no automatic dose dispensers were available as nowadays.
(32) Approaches to monitoring finger doses and positions for wearing dosimeters proposedin the ORAMED project differed from those recommended in Publication 106 entitled'Radiation dose to patients from radiopharmaceuticals. Addendum 3 to ICRP Publication 53'(ICRP, 2008a). The recommendations were based on practices followed in different groupsof centres and it is likely that, in addition to requirements for more optimisation of protection,
dosimetry methods need to be tailored to doses received, especially when they are near thelimit. Recommendations on staff dose monitoring and optimisation procedures will be
provided in Section 8.

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1.7. Education and ongoing training

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(33) Educational programs and ongoing training in radiological protection and safety for
professionals working in a PET/CT facility have three aspects related to patient exposure andthe ALARA principle, occupational exposure to staff, and public exposure. Section 10 will
review the recommendations provided by ICRP and other international organisations,
responsibilities regarding education and training, and training in radiological protection andsafety for health care professionals.

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1.8. Scope

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(34) This publication provides guidance on radiological protection in PET and PET/CT,
giving recommendations on occupational, patient, and public radiological protection.

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(35) Guidance is provided for facility design, including the design of areas for PET
radiopharmaceutical production (cyclotron and laboratory). For staff, advice is provided withregard to optimisation of procedures and dose monitoring. The report covers justification for
PET and PET/CT diagnostic procedures, as well as radiological protection related to the
medical exposure. A chapter on radiological protection of the public attends to the nonnuclear worker and patient-to-patient dose scenarios. Finally, guidance is given for dosemanagement, for development of a quality assurance program, and for education and ongoingtraining in radiological protection for workers in a PET/CT and PET/MR facility.

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1.9. Target audience

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(36) The target audience of this publication includes nuclear medicine physicians,
radiologists, referrers, medical physicists, radiopharmacists, radionuclide laboratory andcyclotron staff, nuclear medicine nurses, nuclear medicine technologists/radiographers,
technical staff, radiological protection officers, patients, hospital and nuclear medicine
department managers, regulatory authorities, equipment manufacturers, and the nuclear
medicine industry in general.

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2. PET AND PET/CT PRINCIPLES(37) Key points in this section:• PET uses a detection principle based on the annihilation photon radiation that follows apositron decay.
• The PET detection principle has the advantage that high resolution can be obtained
without compromising sensitivity.
• Biologically important elements like carbon, nitrogen, and oxygen have positron
emitting isotopes with short half-lives.
• PET is a quantitative technique when all the relevant corrections are applied.
• Originally a complex research tool with limited accessibility, PET has evolved into an
important and widespread clinical modality.
• The combination of PET with CT into one system has been a driving force for theclinical applications.
• PET and PET/CT have important applications within oncology, neurology, andcardiology.
• The short half-life of PET-nuclides requires either an on-site cyclotron, a fast
distribution system, and/or the use of generator systems.

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2.1. PET, principles and technology

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(38) Positron emission tomography as the name indicates utilises for imaging the positron
decay taking place in certain radioactive nuclides with an excess number of protons. Having
lost its initial kinetic energy by interacting with matter over a short distance, the positron will
annihilate with its antiparticle, an electron (from another atom), and create a pair ofannihilation photons, each having an energy of 511 keV corresponding to the particle masses(E = mc2). Due to the law of conservation of momentum and observing that the positronelectron 'compound' (positronium) is almost at rest at the time of annihilation, these two
photons travel in (almost precisely, 180 ± 0.25 degrees) opposite directions, forming forpractical purposes a straight line (Fig. 2.1). Neglecting the travelling distance of the positron
during slow-down, this line is assumed to contain the point of decay. In the following, some
important technical aspects of relevance for radiation doses and protection are described
together with a brief view on today’s clinical applications. For more details the reader isreferred to general textbooks (Cherry et al., 2012; Dahlbom, 2017).

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Fig. 2.1. The annihilation of the positron with its anti-particle, an electron, results in the emission of
two photons of 511 keV each, almost on a straight line.

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DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE(39) The two annihilation photons are detected 'in coincidence'. Since the photons aretravelling with the speed of light, approximately 30 cm ns-1, the relevant time scale here forthe coincidence timing window is ns and fractions hereof. Dependent on the timing propertiesof the detection system such a coincidence event can either just be assigned to the line [Lineof Response (LOR)] or by more precisely observing the time difference between the two
detectors, to a point or interval on that line. The latter is termed 'time-of-flight' (TOF) (Fig.
2.2).

Fig. 2.2. In ‘ordinary’ PET (left), a coincident event is assigned to the line (LOR) between the two
responding detectors with equal probability to all points. In time of flight, TOF-PET (right), theprobability is assigned to a segment of the line based on the measured difference in arrival time to thedetectors.

(40) One major advantage of the coincidence principle is that sampling takes place in all
directions (angles) simultaneously without the need for rotating parts or collimators. This
allows for a high detection efficiency (sensitivity) well suited for dynamic studies, and it alsomeans that spatial resolution can be improved (e.g. by smaller detection elements) withoutcompromising the sensitivity. In nuclear medicine imaging outside PET, where only 'single
photons' are available, imaging requires a collimator with narrow holes to define the directionof origin, and only a very limited fraction of the emitted photons can contribute to the image.
Under these circumstances, any attempt to improve resolution necessarily further reduces thenumber of events that can reach the detector and this trade-off represents a serious limitation
for dose reductions. For typical low energy collimators the detection fraction may be around
0.01%. The similar value for PET early reached 1% and is still increasing (see below).
(41) Another fundamental advantage of PET is, that biologically important elements likecarbon, nitrogen, and oxygen all have isotopes with positron decay (11C, 13N, 15O), but nogamma-emitting isotopes suited for single photon detection. Due to practical limitations ofhalf-life, labelling with 18F (T½ = 110 min) is however preferred, when possible.
(42) Most detected photons in PET do not form part of a coincidence pair but are just'singles'. And not all detected coincident events truly represent a decay position either. Those
which do, are determined 'True coincidences' or 'Trues', but scattered photons may be
detected in coincidence, leading to the assignment of the event to a 'false' LOR (notcontaining the decay point), and two photons from independent decays may by chance be
detected by a detector pair (random events, or just randoms). While for any given object the
number of scattered events is proportional to the number of true events, the number of
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DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

random events scale with the square of the activity and in proportion to the duration of thetiming window. Both scatter fraction and importance of randoms increase with object size,
while the relative number of trues is reduced (Fig. 2.3).

Fig. 2.3. Examples of possible events detected within a coincidence timing window (typically 4–12
ns). Singles are stored for correction purposes (e.g. deadtime) while multiple events (more than two)
usually are discarded. The registration of two coincident events can either be 'true', where the LOR
correctly contains the point of decay, or it can be a 'false' detection. The latter can be either a 'scatter'
event or a 'random' event. When the positron decay goes to an exited state in the daughter nucleus, a'prompt gamma' photon may result: If its energy falls within the acceptance window for 511 keV, or itis downscattered into this window, if can interfere with the annihilation detection.

(43) The above mentioned four PET-nuclides all have positron decays going to the groundstate of the daughter nucleus. In some other, useful, nuclides a fraction of the decay goes to
one or more excited states, and the remaining energy is released as a gamma photon. If the
lifetime of the exited state is short compared to the defined coincidence window, and theenergy lies around or above 511 keV, these 'prompt gammas' may interfere with theannihilation photon detection, also leading to false counts that must be taken into account in
the reconstruction (Fig. 2.3). Examples are 68Ga and 124I. If the life-time is much longer than
the timing window width (e.g. 89Zr) the influence is only through additional singles andrandoms. In both cases, however, calculation for the necessary shielding must include these
additional (higher) energy photons.
(44) Since the necessary subtraction of false counts from scatter and in particular random
events adds noise to the data, this effectively limits the useful count rate that can be obtained
from a system. To describe this effect in quantitative terms, the concept of noise equivalentcount rate, NECr has been defined, basically yielding the corresponding trues count rate that– in a perfect system – would provide the same relative image noise (coefficient of variation)
based on pure Poisson statistics (Strother et al., 1990). After an initial almost linear increase
the NECr curve rises slowly towards a maximum peak at a certain activity (concentration)and then decreases due to dead time effects (Fig. 2.4).
(45) In recent systems this limit (peak) is normally higher than what would be seen inclinical applications for other reasons (availability of radiotracer or limitation of radiationdose to patient). Knowledge of the NECr curve in principle allows for an evaluation of how
efficient the activity is utilised (Watson et al., 2005). In terms of patient throughput, theoptimum would be reached by scanning at or near the top of the NECr curve, with theobvious problem that the count rate is different in different body regions. It is, however, to be
noted that the NECr curve is rather flat. Compared to scanning at the NECr peak, asignificant reduction in activity (hence patient dose) will often only imply a rather limited
reduction in noise equivalent counts, and therefore increase in image noise, which could becompensated by a minor extension of imaging time.

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Fig. 2.4. Example of the relation between trues, randoms and noise equivalent counts (NEC) rates.
The same dataset acquired from a 20 cm cylinder phantom during decay over four orders ofmagnitude in count rate is shown in linear scale (left) and log-log scale (right) high-lighting different
aspects of the relations. On the left, the non-linearity of trues is caused by deadtime. Note that theNECr is much lower than the trues and that it peaks (with a very flat peak) at a much lower activity
than the trues. The break point in all the curves is caused by a limit in the electronics on total counthandling. To the right, the NECr follows the trues at low count rate, the constant ratio reduction beingcaused by the (almost) count rate independent scatter fraction. At low count rate, the slope of the line
for random events is two, while it is one (linearity) for the true and scattered events. Image: Søren
Holm, Denmark.

(46) The requirements for an ideal PET detector are that it should be able to efficiently
stop the 511 keV photons and create a measurable electric pulse with precise information
about the energy and the arrival time of the photon. The detection process thus consists of
two steps: the stopping (and conversion) of the energetic photons, and an amplification of the(light) signal created. While the first part of stopping remains based on scintillation crystalsof different kinds, the amplification part can be made either with traditional photomultipliertubes (PMT) or recently with solid-state based materials. Due to the size and cost of PMTs,
detectors have traditionally been built as an assembly of detector crystals covered with a(smaller) number of PMTs, in a so-called block structure which requires a decoding scheme
similar to gamma camera Anger logic to assign events to a single crystal element (Casey andHoffman, 1986).
(47) To stop the energetic photons a scintillation material with a high stopping power isneeded, which requires a high element number (Z) and a high density. The material should
also convert the energy into low energy photons (visible or UV, 2–3 eV) with high efficiency,
and this process of scintillation decay from excitation must be fast as well. A fast and highsignal from the crystal eases the timing detection, which basically must rely on the first few
light photons that arrive to the 'amplifier'. It is also important in reducing the dead time of thesystem and thereby determines the count rate applicable. While sodium iodide (NaI) is still
the dominant crystal material for most nuclear medicine applications, it is insufficient to stop
511 keV. For many years (1985–2000) bismuth germanate (BGO, Bi4Ge3O12) became thematerial of choice, having very good stopping power (Z for Bi is 83) but less perfectphotons/keV (9) and timing properties (T½ = 300 ns). Most current PET systems use
Lutetium (Z=77) based crystals, either lutetium oxyorthosilicate [LSO, (Lu2SiO5:Ce)],lutetium yttrium orthosilicate [LYSO, (Lu,Y)2SiO5:Ce], or others all having high stopping
power, high density, photons/keV (35) , and short decay times (40 ns).

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DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE(48) Such systems may offer TOF (Surti et al., 2007) and the time resolution has been
improved down to 0.2 ns, corresponding to a spatial uncertainty of only 3 cm (van Sluis et al.,2019).
(49) The advantage of using solid-state amplification [avalanche photo diodes (APDs), or
silicon photo multipliers (SiPM) rest on their smaller size, and the insensitivity to magnetic
fields that make them compatible with MR systems. In particular, SiPM also has less timing
uncertainty on the signal peak ('time jitter') and a potential gain in sensitivity with better
utilisation of the light output from the crystals. One vendor provides a matched crystal-SiPM
system (one-to-one coupling) (Zhang et al., 2018) while others have maintained a block
decoding. One disadvantage of SiPM is a high temperature dependency that requires strict
control of local temperatures with distributed cooling tubes to all elements and potentiallyonline sensitivity corrections.
(50) Signal handling includes validation of the pulse in terms of energy (511 keV),
assignment to a certain detector crystal using a decoding scheme, and decision of a potential
coincidence with any other (relevant) detector element. This requires a scheme for energywindowing at the crystal level and a very precise timing calibration between detectors.
(51) Raw data in a PET acquisition are either stored in sinogram matrices where eachelement corresponds to one LOR (detector pair) and each sinogram contains the informationof one detection plane, or are acquired in 'list mode' where the events are registeredsequentially by writing the addresses of the detector pair together with a time stamp to a data
stream. In this mode, also signals from cardiac and respiratory gating can be included. Afterthe end of acquisition, the list mode data may be 'replayed' and sorted into time frames and/or gating bins without the need to define these before scanning. Random events are either
subtracted online (in list mode during the sorting) or are stored separately for later processing
during reconstruction.
(52) Reconstruction of raw data into transaxial image sets can be performed either bydirect Fourier methods [Filtered back projection (FBP)] or by iterative reconstructions which
are now the methods of choice in PET. When applying all necessary corrections, the PET
images form a three-dimensional quantitative representation of the activity distribution within
the depicted object. The corrections are (among others) for geometry of the LOR’s, dead timeof detector and coincidence electronics, random and scattered coincidences, and attenuation.
The stack of transaxial slices can be resampled to provide sagittal or coronal slices or, forheart studies, the traditional long and short axis representations. For that purpose, an isotropic
spatial resolution is an advantage to avoid any resampling artefacts.
(53) Attenuation correction (AC) serves to restore the signal dependency on depth causedby the higher probability of photon loss through absorption and scatter. In principle, AC in
PET is simple. Due to the fact that each event is created by two photons that together have
travelled through the full length of a LOR, the probability of detection depends only on the
total attenuation properties along that LOR and not on the position of the event on the line.
Therefore, it can be (and traditionally has been) measured using an external source ofmonoenergetic photons in form of a point or pin source rotating around the object, typically68
Ge (annihilation photons from 68Ga) or 137Cs (single gamma photons) A significant
drawback of the external source method was that due to practical limitations of source
strength and count rates for the proximal detector, the noise-optimised acquisition time
almost equalled that of the emission scan and still added significant noise to the final image
in the reconstruction process (Holm et al.,1996).
(54) It was therefore a major breakthrough when PET was combined with Computed
Tomography, CT, to form PET/CT (Beyer et al., 2000). CT can, in very short time, provide
attenuation information that is essentially noiseless. In today’s iterative reconstructions,

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attenuation knowledge is normally integrated in the forward projection step of the algorithm
rather than applied to raw data before reconstruction.
(55) Scatter correction is more complex and less accurate. One of the main methods today
is known as the single scatter simulation technique (Ollinger, 1996).
(56) The development of PET instrumentation has improved the spatial resolution by
providing smaller detector elements, and values of <4 mm are now realistic in a clinicalsetting. The dependency on position in the gantry (centre or edge) and direction (radial ortangential) can be corrected by including into the forward projection of the iteration
knowledge about the point spread function (PSF), the image of an ideal point source (Tong etal., 2010). This can also improve the results from nuclides with high positron energy (like15
O, 68Ga, or 82Rb) where the influence of the width of the PSF is otherwise considerable.
(57) The sensitivity has also been vastly improved. First, by extending the axial field ofview (scanned length of the patient without the patient moving) from 10 cm in early systems(~1985) to 15 cm (~1993) allowing dynamic scans of the whole brain or myocardium, andnext, most important, by the acceptance of inter-ring coincidences (known as 3D). Current
systems are often modular in construction, providing axial field of views of 15–25 cm or
more. Since the sensitivity is almost quadratic in this parameter, an extension from 15 to 25
cm nearly triples the sensitivity. Recently a system has been proposed and built that covers afull body length of 2 m (Badawi et al., 2019). Since a major part of the price of a systemscales with length, systems like that most likely will remain instruments for research andspecial application, e.g. study of whole-body tracer kinetics, while systems spanning 0.5–1 m
are more likely to gain clinical importance.
(58) The axial sensitivity profile when scanning in 3D mode forms a triangle with the top
in the centre slice(s) and approaching zero at the edges. When used for whole body scanningor, actually, as soon as more than one axial field of view is required, an overlap of up to 50%
between adjacent bed positions is used. Recently, systems have been delivered that move thepatient bed continuously through the system with a speed that can be adjusted to the countrate and required image quality in different regions (Osborne et al., 2014). This requires amore complex correction scheme since some corrections are linked to the detector (e.g.,sensitivity normalisation) while others depend on the patient (attenuation and scatter).
(59) From a radiological protection perspective, the most important technicalimprovements are those increasing sensitivity. While higher resolution actually will require
more photons to maintain a certain noise level, and better count rate performance might allow
the patient throughput to be raised by increasing patient activity, the advent of '3D' andincreased axial field of view also makes it possible to decrease the injected activity (patientdose) while still maintaining image quality. TOF-PET may also reduce noise by using theadded position information in reconstruction, a feature sometimes (with a slightly
unfortunately term) marketed by vendors as increased 'effective sensitivity'.
(60) A number of PET systems have been designed or are under development for specificpurposes, e.g. mammography (Raylman, 2018), prostate imaging (Cañizares, 2020), brain
imaging (Akamatsu, 2019), and also a whole range of special animal scanners (e.g. for mice,and rats) are available, but until now the mainstream PET system remains a ring system withbody sized opening (and CT attached).

836

2.2. CT technology

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(61) Almost all CT systems today are so-called third generation systems, where datacollection is made by fast continuous rotation of a balanced arrangement with an x-ray tube

23

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exposing (with a fan beam) an oppositely mounted detector arch. CT images provide thetomographic reconstruction of recorded attenuation of the object.
(62) The attenuation of a material is determined by the atomic composition and the densityof the material as well as the photon energy applied in the measurement. The possibility of an
anatomical interpretation is caused by the fact that different tissues have (slightly) different
atomic composition and density. For a comprehensive description of x rays and CT, see(Mahesh, 2009; Bushberg et al., 2020)(63) While the spatial resolution of CT is inferior to ordinary planar x ray imaging, CT
offers the important advantage of a high contrast resolution without irrelevant 'overlapping'tissues and can therefore distinguish even small differences in e.g. soft tissue. The
reconstructed transaxial images (in CT, unlike PET, often referred to as 'raw data') arepresented to the reader in the scale of 'Hounsfield units' (HU), most often without reference tophoton energy. The value zero represents air, 1000 is pure water, and bone (from spongious
to compact) typically will be represented in the range of 50–1500. Most often, the scale is'clipped' at 3000 HU which may create problems for identifying and describing highattenuation materials, e.g. metal implants and, in particular, dental work.
(64) In early CT systems, the x-ray tube heat capacity and cooling rate was a limitation forscanning extended body regions. This has been solved in some modern tube designs thatallow the rotating anode to be cooled by direct heat transfer, rather than through a radiative
process out of the tube containment. An important correlate to this is that there is no longer a
simple inherent technical limitation to the dose that might be given to a patient during ascanning session and that other guards must be in place to secure against unintended highexposure.
(65) A typical CT session will consist of: 1) a prescan 2) a CT acquisition and 3) thereconstruction of images. The CT acquisition parameters of importance for image quality andpatient dose (to be set before scanning) are: high voltage (kV), tube current (mA), rotation
time, slice collimation, and bed movement per rotation; the latter normally being specified by
the 'pitch', the ratio of bed movement to collimation width. Of course, the selection (from theprescan) of the total scan area is also important. For PET/CT where the PET is operating instep motion, the CT scan in order to allow AC has to cover the full area of PET, which by thediscrete measure could be more than actually clinically requested. One major advantage ofthe continuous motion mode for PET is that it allows limiting the PET scan length, andtherefore the CT scan length, to what is actually needed, hence reducing the CT dosecomponent.
(66) In a subsequent reconstruction, slice thickness and slice distance can be adjusted(upwards) and image matrix size and reconstruction filter (kernel) can be optimised. The
reconstruction, of course, has no influence on patient dose, and the reconstruction parameters
can be freely selected afterwards in repeated reconstructions. Traditionally, CT images havebeen reconstructed using FBP, but more recently iterative reconstruction methods have been
applied also to CT. This allows for reduced image noise and/or a reduction in exposure(mAs), leading to reduced patient doses. One problem still controversial is concerned withthe change in texture of the images that requires some adaptation for the radiologist reading
the images.
(67) Modern systems have automated algorithms that can assist in dose reduction, using
the information from the pre-scan and/or adjusting to data obtained during a scan
(McCollough, 2006; Singh, 2011; ICRP, year2). All major vendors have proprietary
programs (under different names) that can modulate the tube current, either longitudinally
only (reducing, e.g. exposure over the lung region compared to abdomen) or during rotation,observing that the anterior-posterior attenuation in general is much lower than the lateral. The
setting of the algorithm will require the user to enter an allowed mAs interval, an 'image
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889
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quality index' or other information to describe the wanted outcome. It must be noted that, insetting up the scan, a number of pitfalls exist. If the patient is placed off-centre, the prescan
may assume the patient to be larger (or smaller) than what is actually the case and adjust thecurrent accordingly, and if dose limiting shielding (or metal implants) are in the field, thecurrent might be increased beyond the intended if not limited by the user.
(68) Also, the tube voltage may be selected by the system based on calculations on the prescan data. Unlike the tube current modulation, however, the tube voltage is normally kept
fixed during a scan. Recently systems with 'dual energy' capability have been built; these caneither be systems with two complete source-detector arrangements running at different keV, asingle source system with fast kV switching or dual filters, or a software solution that canhandle sequentially acquired data sets.

900

2.3.

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(69) The combination of PET and CT, developed in the late 1990s (Beyer et al., 2000) andintroduced commercially in 2001, marked an important turning point for the use of PET ingeneral. The number of installations grew rapidly, and since 2004 almost no systems havebeen installed as PET only (Jones, 2017). The combined PET and CT systems continue formany practical reasons (including transport into hospital buildings) to be manufactured as
two separate gantries that are mounted together on site, but computer systems and programs
have become more integrated over time (Fig. 2.5).

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PET/CT

Fig. 2.5. One of the first commercial PET/CT systems (Discovery LS, General Electric, 2001) withthe two gantries separated for service. The CT is in front, with the x-ray tube at the bottom and thedetector arch at the top. In the back, the PET gantry is seen with its modular detector assemblies
arranged in a ring around the patient bore. This two-gantry configuration is maintained incontemporary systems. Image: Søren Holm, Denmark.

(70) The added value of CT is twofold: The anatomy information provided by CT is an
important complement to the physiological and molecular information provided by PET. The
combination of the two modalities into PET/CT by placing the two system gantries on acommon axis and with a common patient bed makes it feasible to obtain fused images with25

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the combined information on a single screen and to blend from one to the other by adjusting(colour) scales. In addition, the problem of AC in whole body scans is effectively solved.
(71) The CT image represents a distribution of attenuation values obtained with the actual
CT energy spectrum. To use it for 511 keV requires some modelling and calculations(scaling) (Kinahan et al., 1998; Holm, 2017). In general, this works well, but artefacts may
arise at the presence of materials other than air, soft tissue and bone, e.g., contrast agents,
metal implants, and dental work not included in the simplified model (IAEA, 2014a).
(72) A typical PET/CT session will consist of 1) a pre-scan providing a simple x-ray
projection image, 2) a CT scan, and 3) a PET scan. From a protection perspective it isimportant to stress the significance of the justification for the type of CT scan applied. It is
possible to perform either a full diagnostic scan (potentially with intravenous and/or oral
contrast agents), making a low dose CT scan, mainly for orientation (and AC), or an 'ultralow
dose' CT for AC only. In general, a diagnostic CT with contrast may also be used for AC
although with the potential of (recognisable) local artefacts as well as a minor deviation in thequantitative values of PET (Berthelsen et al., 2005). Therefore, if high accuracy is needed, alow dose scan for AC is performed before the PET, and the contrast enhanced CT after the
PET acquisition.
(73) It should be noted here that the photon flux during a (diagnostic) CT scan can be 4–5
orders of magnitude higher than the emission rate from a patient injected with a typicalactivity for the PET scan, delivering the same absorbed dose to the exposed tissue in a second
as the injected tracer will provide over the lifetime of the activity. The high flux ratio
explains why it is not feasible to perform simultaneous measurement of PET and CT because
the scatter from CT would disturb the PET detectors.

944

2.4. PET/MR

945
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(74) The advent of solid-state amplifiers (APDs or SiPM) for the light output fromscintillation crystals has made it possible to combine PET and MR by installing a PET
detector ring system inside the MR magnet between gradient coils and receiving body coils.
(Delso et al., 2011). The PET electronics is placed behind the magnet and (electrically) wellshielded in a copper Faraday cage to exclude or minimise interference between the MR
radiofrequency signals and the PET pulse handling electronics (Fig. 2.6).
(75) In such a system, PET and MR can be performed truly simultaneously, in contrast to
PET/CT where the acquisitions must be performed sequentially. One major issue in PET/MR
is that, unlike CT, the MR signal and image does not provide an immediate source for AC.
Air filled structures as well as bone have no or low signal from MR and yet these two havethe most different attenuation for the PET photons. For the brain, solutions have now beenfound that works quantitatively satisfying (Ladefoged et al., 2017) and also for whole bodyscans results are normally reasonably accurate (Keereman et al., 2013). For a review of recent
methods, see Catana (2020).
(76) The clinical use of PET/MR is currently limited and specific clinical indications
remain to be proven. One obvious advantage, from a radiological protection point of view if
replacing a PET/CT examination, is that the (often high) radiation dose from CT is avoided.
This is of particular interest in the examination of children. Since the radiological protection
for the PET in PET/MR is not much different from other use of PET, PET/MR will not be
dealt with in detail in this work. For MRI safety, see references in Sections 8, 9, and 10.

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966
967
968
969
970

Fig. 2.6. Example of a PET/MR system with covers removed. The PET electronics is encapsulated ina Faraday cage to avoid interference with MR radiofrequency signals. The water tubes leading into
the gantry provide temperature stabilisation to the PET detectors. Image: Søren Holm, Denmark.

971

2.5. Cyclotron

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(77) The cyclotron principle was introduced by Lawrence in 1930 for accelerating protons(Lawrence and Livingston, 1932). Originally only meant to provide a proton beam forphysics experiments, the possibility of creating artificial radioactivity by bombardment withhigh energy protons was soon detected (Curie and Joliot, 1934). Today the cyclotron is an
essential device for producing the nuclides used in PET and an important integrated part ofmany PET centres (Braccini, 2016).
(78) The basic principle (Fig. 2.7) derives from the fact that a charged particle moving in astationary magnetic field will describe a circular path. The radius of that circle is proportional
to the speed (and energy), hence the rotation time is fixed, dependent only on the strength ofthe magnetic field and the ratio of charge/mass of the particle, but independent of radius. This
holds as long as relativistic effects can be ignored (or internally corrected for by locallymodifying the magnetic field strength) which means that proton energies up to at least 30
MeV, sufficient for most nuclear medicine relevant nuclear reactions, are feasible. The
acceleration is performed by a rapidly switching constant (radio)frequency electrical field(RF, at MHz level) applied at certain gaps in the circle. Between these gaps the particles are
moving in a Faraday cage (named due to their traditionally form as 'D-s'), unaffected byelectrical fields following half-circular paths. The whole process requires a high-quality
vacuum and therefore is contained in a tank equipped with diffusion pumps that can maintaina vacuum of 10-9–10-10 bar. The particles (ions) to be accelerated are extracted from an ion
source at the centre of the cyclotron, by forming a plasma of the relevant gas.
(79) While early cyclotrons actually accelerated protons (or deuterons), modern devices
instead often use H- -ions; a proton with 2 electrons attached is a rather stable configuration.
It has the advantage that the beam exit can be controlled by placing a thin carbon foil at aradius corresponding to the required particle energy. The foil will strip off the electrons andthe shift in the sign of the net charge (from minus one to plus one) will reverse the curvatureof the particles’ trajectory, making it possible to direct them towards the target that has been
prepared for the bombardment process. The target can either be located right next to the
27

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cyclotron tank or accessed through an external beam line that may reach into a shieldedneighbouring room (Fig. 2.8).

Fig. 2.7. The cyclotron principle showing a magnetic field created by an electro magnet, the(electrical) shielding 'D-s' or 'Dees', the oscillator providing acceleration in the gap between the two
D-s and the resulting (proton) path (from a brochure published by the Lawrence Berkeley
laboratories).

(80) Targets can be gas- or liquid based or can be solid targets. A critical part of thecyclotron is the foil separating the cyclotron tank vacuum from the target material. It has tobe thin, not to take out too much energy of the beam particles, yet it should be able towithstand the pressure difference that for a pressurised gas-target may be 20–50 bar. Further,
it must be well cooled to remove the excess energy deposited that otherwise easily could melt
the foil. Transporting the product from gas or liquid targets into radiochemistry hot cells canbe controlled remotely by blowing inert helium or argon gas through thin plastic tubes; theuse of a solid target normally will require access to the cyclotron vault although some
automated systems have been built.
(81) In addition to H- -ions, some cyclotrons are capable of accelerating also deuterons oralpha particles, widening the spectrum of possible nuclear reactions. This requires slightly
modified ion sources and a gas supply of deuterium or helium, respectively.
(82) Commercially available cyclotrons vary in size and performance. Models essentiallydedicated to PET typically range from 10 to 20 MeV of maximum energy of the accelerated
ions (protons or H-), and may have beam currents exceeding 100 μA. Some systems withenergy as low as 7 MeV and relatively low beam current have been proposed. Most of thecyclotrons employed for the commercial production of gamma-emitting radionuclides,
operating at 30 MeV, can effectively produce also 18F and other PET radionuclides. Suchsystems typically have maximum beam currents of several hundreds μA, up to more than 1
mA. A limited number of 70 MeV cyclotrons for commercial production are installedworldwide; these are very important for the massive production of a variety of clinicallyuseful radionuclides, including some of relevance for PET, like 68Ge, the parent of 68Ga.
However, these systems are in general not directly involved in the PET process. Some of the(smaller) PET cyclotrons can be supplied with an integral or a partial (local) self-shield. They
can be installed in rooms with reduced shielding compared to the extensive shielded bunkers

28

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otherwise needed for 'unshielded' cyclotrons. The choice among the available options
depends on the desired production reactions and amounts, taking into account also any
eventual collateral use for research, the needs for maintenance, the use of surrounding areasand inferred dose constraints.
(83) A typical reaction in the target is (p,n) or similar (Table 2.1), where excess energy
from the compound nucleus is removed by (one or more) neutrons. This means that during
bombardment, a high neutron flux will be present around the target (in the cyclotron vault).
Often, the neutrons will be the determining factor for shielding requirements. Further,neutron activation of cyclotron components and building materials is an issue that must be
considered carefully in the planning phase.

Fig. 2.8 Example of a (32 MeV) cyclotron installation comprising a common entrance (with barrier)
to radiochemistry lab and cyclotron vault. A 2 m thick sliding concrete door protects thesurroundings. In the vault is shown the electro magnet (1), the central accelerating circle area (2),diffusion pumps (3), radiofrequency generators (4), extraction systems (5), a target exchange station(6) at one beamline, a second beamline with focusing quadropoles (7) leading into the separate target
room, a diagnostic probe (8) and the cooling water exchange systems (9).

Table 2.1. The 'classical four' cyclotron produced radionuclides for PET.
NuclideHalf-life
Production route(s)
11

C

1052
1053
1054

20.4 min14

N(p,α)11C

13

N

9.97 min16

O(p, α)13N

15

O

2.04 min15

N(p,n)15O or 14N(d,n)15O

18F

109.8 min18

O(p,n)18F (F-) or 20Ne(d,α)18F (F2)(84) As an alternative to local cyclotron production, some radionuclides can be obtained
from generator systems based on more long-lived nuclides. The most important, and29

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1055
1056

currently only commercial, systems are the 82Sr/82Rb and 68Ge/68Ga generators. Interestingly,
these generators were known and applied as early as in the 1960s.

1057

2.6. Clinical applications and radiopharmaceuticals

1058

2.6.1. Neurology

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1082
1083

(85) The first applications of positron coincidence imaging were (technically) limited tothe brain (Brownell, 1968) using, e.g. 74As arsenite (T½ = 17.8 day) or 64Cu labelled EDTA
(T½ = 12.7 h) for tumour detection. The early studies with ring PET systems, also for brain
only, used inhaled 77Kr (Yamamoto et al.,1977) or [15O]CO2, and later 15O labelled water as
brain perfusion tracers. In combination with [15O]O2 and [15O]CO the cerebral oxygen
consumption (CMRO2) could be determined. During the 1980s and early 90s, PET was still
primarily used for research in the brain, e.g. activation studies with [15O]H2O, a field takenover by the non-ionising method of functional Magnetic Resonance Imaging at the end of the90s. The study of brain receptor systems e.g. dopamine and serotonin also became importantresearch applications and remains so.
(86) 2-[18F]FDG can be used to measure the glucose consumption of the brain, and much
effort in the 90s was put into its quantitative determination, but due to the high complexity
this never got a clinical impact. Compared to its use in the rest of the body (see Oncology
below), 2-[18F]FDG is less useful for tumour detection in the brain due to the highphysiological uptake in normal tissue.
(87) PET and PET/CT today has important clinical roles in neurology:• For neurodegenerative disorders particularly 2-[18F]FDG and radiotracers for thedetection of amyloid accumulation in suspected Alzheimer’s disease are in clinical use.
• In Parkinson’s disease a number of tracers are gradually being introduced: 6[18F]FDOPA, [18F]FE-PE2I.
• In brain tumours radiolabelled amino-acids are used for glioma, 11C labelled
methionine, 6-[18F]FDOPA and [18F]FET. [68Ga]Ga-DOTA-conjugated peptides arebinding to the SSTR2 receptor in meningiomas.
• Finally [15O]H2O is (still) used to estimate the cerebral hemodynamic reserve capacityin chronic cerebrovascular disease.

1084

2.6.2. Cardiology

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(88) Through the early advent of systems with an opening that allowed scan of the body
(Hoffman et al., 1976), the heart became another important target for PET research. The
primary topics are myocardial perfusion and metabolic uptake of different substrates. The
main clinical condition is the assessment of 'viability', where regions of the heart show
reduced perfusion while (glucose) metabolism is still preserved, indicating that the patient
might benefit from an intervention (revascularisation) with the intension of restoring theperfusion (Schelbert, 2002).
(89) The PET tracers in common and competing use for quantitative determination of
myocardial perfusion are 15O labelled water [15O]H2O, 13N labelled ammonia [13N]NH3 and[82Rb]RbCl2. While 15O and 13N are cyclotron products, [82Rb]RbCl2 is injected directly froma generator system eluted with saline, which makes it available for a more widespreadclinical use. [15O]H2O is often considered the reference tracer because it is the most direct
measurement. It is metabolically inert, essentially freely diffusible, and has an extraction

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fraction close to one up to very high perfusion values. Rubidium is taken up as a potassium
analogue, and the uptake is non-linear in perfusion. [13N]NH3 is taken up and retained byvarious metabolic pathways and the resulting signal is influenced by several variables,
including perfusion, extraction fraction and metabolic status. Due to the difference inpositron energy (range) as well as half-life, image quality with rubidium and [15O]H2O isinferior to that of ammonia; for [15O]H2O often only the calculated perfusion values will be
used. A major advantage of the shorter half-life, however, is that it is possible to repeat
examinations (rest - stress) with a short time interval completing a full examination within
half an hour. More details can be found, e.g. in European Association of Nuclear Medicine(EANM) guidelines (Sciagrà et al, 2021).

1108

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(90) The majority of all PET/CT scans are performed on oncological indications, andprimarily using 2-[18F]FDG as the standard tracer. 2-[18F]FDG whole body scans are used for
diagnosis, staging, radiotherapy planning, response to therapy and assessment for recurrence.
Some details for production of 2-[18F]FDG and patient handling are shown in Section 3, anddue to its importance, most examples in this publication refer to this tracer.
(91) Other tracers with more specific indications have been developed and come into
routine use like 68Ga or 64Cu labelled somatostatin receptor ligands(DOTATOC/DOTATATE) for neuroendocrine tumours or 68Ga labelled peptides to prostate
specific membrane antigen (PSMA) imaging in prostate cancer (metastases).

Oncology

1118

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1120
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3. PET/CT FACILITY DESIGN(92) Key points in this section:• Cyclotron vaults should be planned and constructed primarly to protect against
secondary neutron radiation and concrete is the primary material normally used.
Shielding requirements will depend on the incorporation of self-shielding.
• Radionuclide transfer systems within a cyclotron facility should be designed tominimise leakage and staff exposure, and pressures and airflow designed to limit
spread of any airborne contamination.
• Handling of PET radiopharmaceuticals during synthesis, filling vials and dispensing inshielded syringes should be automated as much as possible.
• Patients remain in the PET facility for several hours including a rest period following
2-[18F]FDG administration that may be 60 minutes. Planning movement of the patient
through the department to minimise exposure of staff members is crucial.
• The provision of shielded rooms for resting patients, the location of active toilets tominimise distances of any patient movement, and the siting of patient facilities
adjacent to the scanning room are all important.
• PET/CT facilities require shielding against almost continuous low dose rate exposure
from 511 keV photons emissions and short higher dose rate CT x-ray exposures.
Protection of walls against 511 keV photons using concrete will dominate shielding
requirements, but scattered CT x rays must be considered for the scanning room doors
and windows.

1140

3.1. Types of PET/CT facility

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(93) Radionuclides used in PET imaging have relatively short half-lives and are mainly
produced using cyclotrons. 18F is the mainstay for PET studies and it has a half-life of 110
minutes, so a PET imaging facility without a cyclotron of its own needs to be located with aproduction centre within a few hours transport distance (Ducharme et al., 2009). Facilities ofthis type carry out scans using primarily 2-[18F]FDG, but may supplement this with otherradiopharmaceuticals labelled with 18F (such as [18F]NaF, [18F]Choline, [18F]-PSMA,[18F]FLT, [18F]-DOPA) and positron emitting radionuclides produced by generators, such as68
Ge/68Ga, 82Sr/82Rb. This type of facility requires laboratory areas for labelling ofradiopharmaceuticals using either a commercial kit or synthesis module (IAEA, 2010).
(94) Other PET radionuclides such as 11C, 13N, or 15O, with half-lives of about 20, 10, and2 minutes respectively, can only be used if there is a cyclotron on-site. Therefore, specialist
PET facilities usually have a cyclotron incorporated into the same building. A facility of thistype with its own cyclotron that produces 18F and other common positron emitting
radionuclides for use within the facility can use a variety of automated modules for synthesisof different radiopharmaceuticals that are commercially available. These are installed inlaboratories located near the cyclotron, within 'hot cells' suitably shielded and equipped with
the necessary ventilation and safety systems. All radiopharmacies must meet stringent
requirements arising from drug legislation as regards the facility infrastructure, quality of air,finishes, flows of staff and products, etc, involving the design of the site. Furthermore, eachcentre should establish an extensive quality assurance system in order to guarantee thequality, safety and efficacy of the products. According to local regulations, the requisites for32

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facilities that produce radionuclides for distribution to other centres may be more stringent.
Radiological protection of cyclotron radiopharmaceutical production facilities needs to take
into account good manufacturing practice (GMP) requirements for the use of such products inhumans and in accord with the specific jurisdiction (FDA, 2011; Vidal et al., 2020; EC,2022).
(95) The majority of this document will be devoted to the design and operation of a PET
scanning facility applicable to all types, but some discussion will be included at the start
relating to centres with cyclotrons.

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(96) The cyclotron vault should be planned and constructed primarly to protect against
secondary neutron radiation produced during irradiations, while paying attention to theprompt gamma radiation resulting from the de-excitation of nuclei following interactions
with the beam (IAEA, 1988; NCRP, 2003). Absorption of neutrons will require a material
with significant hydrogen content, while attenuation of gamma radiation will require high Z
materials. Concrete is used predominantly, given the favourable balance between attenuation
capacity, mechanical and structural strength, availability and cost. Type and thickness of thewalls will depend on the make, model, and energy of the cyclotron, and whether or not there
is a self-shielding component.
(97) The level of risk associated with this class of accelerators is dependent on theposition and distribution of the shielding. When the cyclotron is supplied with a factory
designed shielding, entirely surrounding it, this is termed as a self-shielded cyclotron (Hertel
et al., 2004). If part of the shielding is placed only around the target stations, this is termed a'local shield' (Infantino et al., 2017); in many cases however the shield is included only in thevault walls (Mendez et al., 2005). Self-shielded or locally shielded cyclotrons require a lower
level of additional shielding, but nevertherless they need to be placed inside a vault toprovide additional shielding (NCRP 2003; Schmor, 2011). The choice of the type of
cyclotron and shielding, and the overall design of the facility will depend on the intended use(Marengo et al., 2023). Where research is to be undertaken on different radionuclides, thespace required will depend on the dose constraints applied for staff and the public, and theprospective plans for future decommissioning (Braccini, 2016).
(98) In addition to the cyclotron vault, rooms for the cabinets containing the electronics,
the cooling system, and the control system, and other equipment associated with thecyclotron, will be needed, as well as for storage. Gas cylinders required for the operation(including high purity H, He, N, and others) are typically located in an external area, close to
the vault (IAEA 2009a).
(99) The high level of radiation produced during cyclotron irradiation, together with themagnitude of the activity levels generated, and the amount of processing involved require
extensive radiation safety measures to ensure staff safety. These measures include: systems toensure that an operator cannot become trapped inside the vault, automated equipment tominimise personnel handling of radionuclides, the extensive use of shielding and safety
interlocking devices, a specific ventilation and air conditioning system, and the radiationlevel monitoring system to protect personnel and the environment (Mishani, 1999; Sharma,
2006; Alwani, 2016; IAEA, 2020a).
(100) PET Cyclotrons produce radionuclides through bombarding a suitable target with 1H(p) or 2H (d), that involve nuclear reactions such as (p,n), (p,2n), (p,α), (d,n), etc. In
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cyclotrons for the production of PET radionuclides, the primary beam of charged particles
will be completely absorbed by the target. Neutrons produced in nuclear reactions are themost important secondary radiation, even if protection against gamma photons is also
required. The radiation field created around the cyclotron will vary with the type of target
material, the beam current and the maximum energy used (Vega Carrillo, 2001). The neutron
dose rate produced by a modern cyclotron - target system, which is not self-shielded, duringhigh current irradiation, will exceed 10 Sv h–1 at a distance of 1 m from the target (Infantino
et al., 2016), and the cyclotron manufacturer can provide information on this. Full details of
the fields that occur, both during and after operation, which will aid in the design andspecification of shielding can be obtained in the literature (IAEA, 1988; NCRP 2003).
Concrete is largely used for shielding, granting sufficient hydrogenous content to attenuate
neutrons, whilst having suitable protection characteristics against gamma photons. Materials
used for the self-shield or local-shields include: concrete, water, heavy concrete, e.g. loadedwith Limonite (an iron ore), and Iron; these are frequently added with some material
including boron, which has a high capture cross-section for neutrons and the energy of thecapture gamma photon emitted (478 keV) is lower than that from the hydrogen interactions(2.2 MeV). For these systems, the cyclotron manufacturer should provide details of theradiation fields that occur during operation, and information on the activation.
(101) New systems and methods are continually being developed, so a literature review
should be undertaken to identify the most recent techniques used for operation andproduction processes, and appropriate waste streams. The vault will normally be at ground orbasement level to facilitate shielding and minimise structural support issues. The productionof neutrons in nuclear reactions at the energy levels of PET cyclotrons is essentially isotropic.
The groundshine and skyshine effects should be appropriately accounted for (IAEA, 1988;
NCRP, 2003).
(102) Calculations of shielding requirements for cyclotrons may use a formalism similar to
those involved in radiotherapy linacs (NCRP, 2003), once the appropriate data for neutron
HVLs or TVLs are selected. Monte Carlo methods have proven to be highly useful in thecalculation of wall shielding, and provide more accurate results with respect to analyticalmethods in the calculation of the doses transmitted through mazes and conduits (Infantino etal., 2017; Facure and França, 2010). The primary purpose of the shielding is to reduce theneutron flux during cyclotron operation. A typical thickness could be 0.5–0.6 m of concrete
for a 10–11 MeV self-shielded cyclotron (Pant and Senthamizhchelvan, 2007; Masumoto etal., 2014), and of the order of 2.0–2.4 m of concrete (density 2.3 g cm-3) for a non-shielded
18 MeV cyclotron (Facure and França, 2010; Infantino et al., 2017). However, these values
are purely indicative, being influenced by the type of target and beam current, local
workload, and distance from walls. Shielding that will reduce the neutron flux to an
acceptable level will provide adequate protection against the gamma flux. When designing
the shielding consideration should also be given to possible future upgrades to the cyclotron,such as increased beam current (e.g. new ion sources) or new targets that would increase the18
F production and therefore increase neutron flux through the reaction 18O(p,n)18F. The
shielding should be tested using a reaction which produces a high neutron flux to ensure thatthe protection is sufficient; typically the 18O(p,n)18F reaction is the preferred benchmark.
Since not all activation reactions generate equal intensities of neutrons, an assessment of theradiation dose made during an irradiation of a target for the production of 13N or 11C would
severely underestimate the flux of neutrons.
(103) Many vaults will have a shielded door (Heaton et al., 2014), although a maze isfavoured in some cases (Russo et al., 2011); prospective evaluation using Monte Carlosimulations, when possible, can be helpful in making the optimal choice between the options
available (Facure and França, 2010). The drive mechanism for the door should be located on
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the outside of the vault to facilitate repair if stuck in the closed position (Heaton et al., 2014).
The light signalling system can include a series of gradual alarms activated by the subsystemsof the cyclotron that are progressively turned on. As an example: a green light indicates that
all the subsystems are off or in standby mode; Magnet ON is frequently yellow,
Radiofrequency ON is typically orange, BEAM ON is red. However, this light coding is notstandardised. The door can be opened via a local control panel; this usually produces anadditional luminous and acoustic signal to indicate 'moving door'.
(104) The cyclotron will have interlocks and incorporate fail-safe (last man out) buttons, toconfirm that the vault is clear of personnel when the cyclotron is in operation. A visual
control system, based on radiation-resistant cameras, is recommended, and if combined witha movement detection system it can further increase safety, avoiding the possibility of
trapping an operator in the bunker (ICRP, 1997b).
(105) Other aspects that should be considered include firefighting systems, that should bebased on extinguishing gases, since the use of liquid or powder extinguishing media could
damage the cyclotron irreparably. Since the beam is generated from hydrogen or deuterium
gas, there should be a detection system for any gas leaks, which could cause explosions. A
flood detection system can be useful in order to avoid damage to the accelerator and also to
avoid the possible spread of contamination. The level of illumination in the vault should be
adequate for ensuring proper maintenance.
(106) Access to the bunker should be regulated. During irradiation, access to the bunker ofa cyclotron that is not self-shielded, or that is only locally shielded, must be impossible. In
the case of self-shielded cyclotrons, for some models operating at proton beam energies of
10–11 MeV, the levels of environmental dose rate during irradiation are of the order ofseveral tens of µSv h−1; access could be allowed even in the irradiation phase. However, theactual need for such access should be carefully evaluated and strictly regulated; what has
been said does not apply in any case to self-shielded cyclotrons operating with higher beamenergies. Access to the bunker should require that the operator wear specific work clothes
and use gloves and face masks. For the maintenance operations carried out inside theacceleration chamber of the cyclotron, these requirements can be more stringent, in particular
to avoid the inhalation of contaminated or activated dust (Calandrino et al., 2010; Terranova
et al., 2011; Biegała et al., 2022), as well as for the protection from beta radiation that could
arise from some components.
(107) The concrete used for shielding the vault will contain some components that can be
activated with half-lives ranging from a few hours, such as 24Na, up to years for 60Co and152
Eu (Birattari et al., 1989; Calandrino et al., 2006, 2020; Martinez-Serrano and Díez de losRíos, 2010; Vichi et al., 2019). The level of long-term activation will depend strongly on theworkload of the accelerator and on the composition of the concrete and may become aliability when a facility is decommissioned. Whenever possible, a low alkali grade concreteshould be used to minimise activation through neutron capture reactions and reduce doses tocyclotron workers. Iron reinforcement bars should be placed at a depth greater than 30 - 40
cm in the concrete, to reduce activation (Vichi et al., 2019). Addition of neutron absorbing
components, such as colemanite or borosilicate glass powder could be considered, provided
that the mechanical characteristics of the concrete are preserved (Gunduz and Usanmaz,
1986; Gencel et al., 2010; Korkut et al., 2010; Korkut et al., 2012; Okuno, 2005; Jang et al.,2017). Additional shielding around the target could be installed to avoid unnecessary
activation of the concrete shielding, and will determine the level of activation of the 'local'
shield.
(108) It is important to consider at the planning stage the ease with which a cyclotron
facility can be decommissioned, as this can save a considerable amount of work and expense
later by reducing the amount of radioactive waste generated when the facility is replaced. If
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there is a service access to the vault through which the whole cyclotron can be removed, thiswill avoid the expense of having to cut up the main magnet. The planning of the vault in sucha way as to minimise the activation will also be beneficial (Paans and de Jong, 2017; Tesse etal., 2018; Vichi et al., 2020). Use of non-metallic reinforcement will reduce the possibility ofactivation. The outer layers of concrete (away from the cyclotron) can often be disposed of as
regular waste whereas the inner layers will probably be low level radioactive waste if they
contain iron reinforcement, but could be removed and disposed of more easily duringdecommissioning if they do not contain metal, in the form of a strippable layer of concrete or‘sacrificial layer’ (Eppinger et al., 2001; IAEA, 2016; Lee et al., 2019;). Therefore, carefulplanning of construction and use of layers of material on walls and floors that can readily be
stripped away will significantly reduce the mass of concrete for final disposal.
(109) All surfaces within the vault should be hard, washable, and smooth, and either
painted or covered with an epoxy coating, to minimise the creation of dust and allow any
contamination to be removed easily. It is important that dust is kept to a minimum as this canbe a means through which radioactive contamination is transported out of the vault.

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(110) The pattern of air flow within a facility should be designed to control airborne
contamination. All the active part of the ventilation system should be redundant, in order togrant proper function even in conditions differing from those originally planned. The fans for
air expulsion should be placed after the filtering systems. Filters should be adequate for thetypes of effluent. In general, high efficiency particulate air (HEPA) filters or ultra-low
particulate air (ULPA) filters are requested; in addition, activated charcoal or othersupplementary filters can be necessary for specific products. The ventilation system should
be designed to avoid re-circulation of air in normal working conditions. Air outlets and inlets
should be positioned so that expelled air is not recirculated. In the internal laboratories, theflow of ventilation should normally be directed from the top downwards, to avoid
resuspension. Air outlets should normally be placed at low levels and the airflow should befrom areas where there is minimal likelihood of airborne contamination to areas where suchcontamination is probable. Room air from a radiopharmacy or radiochemistry laboratory
should be vented through a filtration system or other mechanism for trapping airborne
radioactive materials and should not be recirculated, neither directly, in combination withincoming fresh air in a mixing system, or indirectly, as a result of proximity of the exhaust toa fresh air intake. The possibility for competitive airflow should be considered in the design(IAEA, 2020b; EudraLex, 2020).
(111) In general, the cyclotron vault should be at the lowest pressure, the hot laboratories
at an intermediate pressure, and the surrounding public areas at a higher pressure. For reasonsof asepsis, some radiopharmacies may need a positive rather than a negative pressure withrespect to the surroundings (IAEA, 2018; Eudralex, 2020). In this case, the pressure gradientcan be obtained by locating other workstations/areas at negative pressure next to theradiopharmacy workstation/area. As an example, the entrance air lock and the technical spacebehind the hot cells can be at a negative pressure, with respect to the clean room whereradiopharmaceuticals are synthesised and dispensed under conditions that meet a specified
level of air quality.
(112) The general control for the ventilation system should be placed in an external, easily
accessible area, kept clear in order to facilitate intervention. Internally to the laboratories
there should be regulation controls, measuring devices, alarm signals, and displays of thelocal relative pressure. In emergency conditions, an emergency push-button for reactivation

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of the ventilation system should be provided, in order to avoid dangerous levels ofcontamination inside the premises.
(113) Minimising radiation exposure is paramount in the design of a facility throughprovision of a smooth flow in processing. One way of achieving this is by ensuring that areas
where successive steps are carried out are adjacent to each other; vented pass-through boxes
may help to avoid disruption of the air cleanliness required for processing pharmaceuticals.
(114) The delivery of radionuclides in liquid or gaseous form from the targets, within thecyclotron bunker, to the points of use must be done via a shielded transport system. The
fluids can be transferred using an inert carrier gas (IAEA, 2009a, 2012). The passage ofdelivery lines through walls or in trenches under the vault floor provides an effective meansof moving material from one area to another with essentially no possibility of irradiation. The
radionuclide activities they carry are likely to be large, so they will need to be shielded
appropriately. The level of shielding is typically the order of 0.3–0.5 m of concrete, or 5–10
cm of lead, but this will depend on the distance from areas where staff have access, theoccupancy of these areas and transit times.
(115) In order to minimise the possibility of spreading contamination, the radionuclidetransport lines should be tight, controlled and replaced regularly at agreed intervals of time,taking account of the deterioration caused by the radiations to which they are exposed;
arrangements should allow this to be done without the need for lifting of heavy shields.
Safety interlocks should be in place, in order to avoid delivery to a hot cell that is not in asafe condition (e.g. with door closed, ventilation active, and synthesis module ready toreceive the radionuclide).
(116) Penetrations through the walls of the vault, either for flow lines, ventilation,
electrical supplies or other services should avoid any direct line of sight through which
exposure might occur. Monte Carlo modelling is useful for planning and verifying design
proposals (Infantino et al., 2016). This can be achieved by running penetrations at an angle orusing an S-shaped curve (IAEA, 2009a). Curved plastic pipes may be set into the concrete
walls or floor at installation to act as conduits.
(117) Components of the cyclotron will be activated by proton interactions, if they are hit
by the beam or in close proximity to it, or irradiated by secondary neutrons produced in thetarget. Components of the extraction system (the 'deflector' and the 'septa') in positive ion
cyclotrons will be activated significantly.
(118) In modern cyclotrons accelerating negative ions, the design will aim to reduce
activation to a great extent. The most activated components will be the targets, in particular
the foils used to seal the target with respect to the vacuum chamber. The foils are crossed by
the beam, so their activation is significant. The material used most frequently is Havar, analloy of cobalt, chromium, iron, tungsten and others. A variety of radionuclides are produced
in Havar foils: among many others, the most relevant are 51Cr, 57Co, and 54Mn. The extraction
system will also be activated. In negative ion cyclotrons, the principal components aregraphite foils, in which only short-lived radionuclides will be produced. However, the foils
are typically mounted on an aluminium or other metal frame, and the whole assembly could
be hit by the tails of the beam, or by stray protons, resulting in activation. Another site where
activation may occur is the collimators, used to shape the beam before it enters the target.
The collimators typically absorb a current of the order of 5–10 % of the beam current, whichmeans several µA, and depending on the material, activation can be significant. Collimators
are typically made of a high melting point material. Tantalum is an excellent collimator
material, since even a very limited thickness stops the beam tails completely, but it produces
significant activation (181Ta, 182W). Graphite is much better in terms of reduction ofactivation, but a greater thickness is necessary. Other internal components in copper, may be

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activated with Zn (Calandrino et al., 2006, 2020; Marengo et al., 2008; Terranova et al.,2011).
(119) Dose rates at a distance of 1 m from targets after 18F production can be of several
mSv h−1, decreasing to levels of hundreds of µSv h−1 several hours after production of 18F, so
the standard practice might be to carry out any work on targets after the weekend or holidays,in order to allow a reasonable time for decay. For maintenance inside the vacuum chamber ofthe cyclotron, targets should be disconnected and removed, to avoid unjustified exposure.
After that, in negative ion cyclotrons, the dose rates in close contact with internal components
will be limited to a range of several tens of µSv h−1, particularly if collimators are made fromgraphite (Calandrino et al., 2010).
(120) During maintenance operations within the vacuum chamber, care is needed inminimising the possibility of contamination. Residuals and powders coming from all thecomponents previously reported could be present, and the possibility of inhalation cannot be
excluded. All maintenance operations should be carried out bearing this in mind; operators
should wear proper protective clothes, gloves, and a face mask. A point that requires attention
is cleaning of the ion source, when this is internal to the cyclotron. The ion source body isrelatively far (30–50 cm) from the targets, so that any activation comes only from secondary
neutrons. The body of the ion source, typically made of brass, needs to be scrubbed toremove residues. During these mechanical operations powders are produced, that present a
potential hazard from inhalation. The deposits on the ion source body come from tantalum,
the main component of the cathodes, and contain 182Ta, due to the (n, γ) reactions in 181Ta,
induced by the secondary neutrons. The ion source can be disengaged and cleaned in alaboratory area, within a vented hood (Calandrino et al., 2010; Terranova et al., 2011).
(121) 40Ar is a natural component of air. Given the high cross section for thermal neutron
capture (40Ar(n, γ), σ = 600 mbarn), 41Ar is produced in the air of a vault and the amount
depends on the total volume of air irradiated. In fully self-shielded cyclotrons, this volume
will be limited. In 'naked' cyclotrons, the whole internal volume of air is significantly
irradiated with thermal neutrons, and the production of 41Ar will not be negligible.
Nevertheless, it has been shown that the concentration of 41Ar in the air exhaust is very low,
and the radiological consequences for the public in the surrounding areas are not significant(Birattari et al., 1986; Infantino et al., 2015; Cicoria et al., 2017; Fischer et al., 2019).
(122) The target assembly, that is the body and device holding the target material, areessential components in a modern cyclotron, in order to produce clinically relevant amountsof the radionuclides. Concerning safety aspects, targets should be tightened, in order toprevent any release of radioactivity during irradiation. Most cyclotron control systems
provide for a quick tightness test prior to each irradiation. In addition, the target tightness
should regularly be fully checked by pressurising each target with inert carrier gas. Targets
should be periodically dismounted, cleaned and worn components such as foils, gaskets andseals should be replaced. After disconnecting a target, a period of 'cooling down' to allow for
decay of radioactivity, storing the target in a shielded container, is recommended. For thisreason, a PET Cyclotron centre should always have spare target assemblies, for replacement.
After appropriate 'cooling down' (e.g. 2–4 weeks), the target assembly can be disassembled.
The foils will be the most activated component. They should be quickly removed, using
tweezers or other tools to avoid contact with fingers, and disposed of in a shielded container,
before proceeding with any further operation (O’Donnell et al., 2004; Ledesma et al., 2008).

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DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE(123) The PET Radiopharmacy should be close to the cyclotron, so that the distance fortransfer of radionuclide from the target to the hot cell is as short as possible. Several different
areas or laboratories will be required for production, quality control, research, preparationand packing if radiopharmaceuticals are to be sent to other facilities (IAEA, 2009a).
Production operations should take place in shielded hot cells, with shielded lines used fortransfers between cells, using automated systems. A facility producing radionuclides for
distribution to other centres will also need an area for packaging radiopharmaceuticals for
dispatch to other centres. Appropriate authorisations, licences, or permits will be required inevery country relating to radiation and pharmaceutical production regulation (IAEA, 2009a;
2010; Russo et al., 2011; Heaton et al., 2014).
(124) Nowadays, most manual operations on radiopharmaceuticals can be assisted, if not
replaced, by automated operation. Appropriate devices are available to perform synthesis,
filling vials and dispensing in syringes, with minimal if any need for manual intervention. In
particular, dispensers to automatically fill the final unit dose in a syringe are now available
not only to be installed within dedicated hot cells, but also as 'stand alone' dispensers that can
fit in almost any type of cell or workbench. These systems, in addition to standard
radiological protection measures in radiopharmacies, make it possible to minimise staff
doses. Purpose built commercial hot cells are available, with 3.5–10 cm thick lead shielding
depending on the activities to be handled, and finished in stainless steel to facilitate
cleanliness and sanitation. The synthesis modules for radiopharmaceutical production areplaced inside the hot cells and require controlled environmental conditions and supplies ofgases, such as helium, compressed air, or nitrogen. Therefore, the design and location of the
hot cells should be planned, to ensure they are sufficient in both number and size toaccommodate the synthesis rigs required for the range of radiopharmaceuticals to be
produced.
(125) The hot cells are normally operated at a low pressure to reduce the possibility ofleaks into the laboratory (Russo et al., 2011). The stainless-steel box in which synthesis
modules or dispensing devices are installed should be tightened and specifically tested andcertified at the factory.
(126) In the event of malfunction of a synthesis module, such as a break in a connector ora leakage in the reactor vessel, there can be a significant loss of radioactivity within the hotcell. Each hot cell should have a monitoring system aimed to control all operation conditions
like temperature, pressure, air flow inside the cell, including monitoring of radiation levels
inside the cell and in the exhausted air. The control system of the hot cell should include aninterlock to ensure safe operation: delivery of activity should be possible only if the hot cellis in a safe condition and 'ready' to receive the activity; the door of the hot cell should notopen if the level of activity contained exceeds an agreed threshold; ventilation should bevariable according to the needs; in case of a leakage of radioactivity, such as a gas or vapour,there should be a feedback system based on monitoring, controlling the ventilation system(e.g. stopping the ventilation and activating a containment system). Routine releases of gases
from the synthesis modules should be collected elsewhere, as explained in section 3.3.2.
(127) The production of liquid radioactive waste by a PET Radiopharmacy Laboratory
should be substantially reduced so that it is a minimum. Small volumes of liquid waste can beabsorbed on a specific substrate, and so converted into solid waste, the management of which
is preferable.
(128) Some PET tracers such as 82Rb and 68Ga are obtained from elution of generatorsstored on site. 82Rb generators are typically installed within a specific infusion system. They
should always be eluted according to the procedure indicated by the manufacturer, using theappropriate eluate and testing method.

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(129) Ga generators should be installed within a hot cell; even if manual elution is
feasible, the use of an automated or semi-automated system will reduce dose to theextremities of operators, while granting repeatable operation (Boschi et al., 2012, Heaton etal., 2014) eluates should be checked for breakthrough of 68Ge (Cicoria et al., 2009).
(130) The final dispensing of radiopharmaceuticals in the syringe for injection to patientscan be performed either in the PET Radiopharmacy laboratory, or in the clinical area, in ashielded cabinet. Independent of the location, dispensing is an activity that involves asignificant exposure to the hand of staff (Kolaard et al., 2021; McCann et al., 2021;
Andriulevičiūtė et al., 2022), as well as the possibility of contamination. The use of an
automatic dispenser, that fills syringes already fitted with a shield reduces the exposure to aminimum. For other details on the injection procedure see Section 3.5.2.

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3.3.2. Release and monitoring of radioactive gases

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(131) In addition to the neutron activation of the bunker air and the production of 41Ar,
there are two main sources of production of gaseous radioactive effluents: the cyclotron,
including its targets, and the modules for the synthesis of radiopharmaceuticals.
(132) Release of radioactive gases can occur from the cyclotron vault, in several different
ways. Some of the materials that are irradiated are gases, as in the case of the production of
11
C and 15O, but the majority are liquids, such as for 18F and 13N, and these are held withintargets that are sealed assemblies that, in normal routine use, should not release any
radioactivity. Target rupture, that is breaking of the foils in the target, generally is followedby the containment of the volume of target material inside the vacuum chamber of thecyclotron, with limited if any release to air. The latter may happen through the helium
cooling system or the pumps in the vacuum system; to take account of this, the outlets of the
He compressor and mechanical pumps could be connected to a containment system or to agas waste delay line. A delay line can simply be a length of tubing, that is sufficient to createa transit time for gases, that will provide a substantial amount of decay in radioactivity.
(133) Release of radioactivity to air may occur if the target assembly, or a valve of thetarget filling/voiding station, or the delivery line are not as tight, as they should be. Since a
rupture or defect in these components due to wear cannot be excluded, prevention is the only
way to minimise risk. Checks of tightness of all components that may potentially leakradioactivity should be included in routine testing procedures.
(134) Routine release of radioactive gases during synthesis of radiopharmaceuticals may
occur in different phases, and strongly depends on the type of process. It is important toconsider first of all the production of 2-[18F]FDG. In the delivery of the irradiated bolus of18
O enriched water from the target to the synthesis module, the carrier gas (typically a flow of
He or N) is generally transporting some 13N produced by the cyclotron during 18F production,
due to the (p, α) reaction on the residual 16O. The carrier gas flows in the module and can becollected at an exit point that depends on the technology of the module. Some types ofmodules have an output fitting for collection of exhaust gases 'pushed out' by the cyclotron;in other types of modules there is a vacuum pump that sucks the bolus, and the output stageof this pump is the release point. In any case, the emission point should be appropriately
identified and connected to a collection system. Other potential phases of gaseous releaseduring the synthesis of 2-[18F]FDG are the processes happening in the reactor vessel of themodule. The total volume of gases released is typically of the order of a few litres. If notcollected properly, these gases may contaminate a much larger volume of air, used inventilation of the hot cell. Appropriate solutions are the collection by means of plastic bags
(Schweiger, 2001), or the connection of the exhausts to a gas delay line. The above

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indications provide useful guidance for all other processes of synthesis of 18F- based
radiopharmaceuticals.
(135) The issues may be more complex in the case of the production of 11C
radiopharmaceuticals. Given the variety of products and synthesis modalities, it is notpossible to give simple, straightforward indications. In general, the volumes of gases arehigher than in the production of 18F in liquid phase. All possible release points from asynthesis module should be identified in advance and fitted with a sequence of chemical traps
based on Ascarite, sodium or potassium hydroxide, molecular sieves, and finally activatedcharcoal.
(136) Nevertheless, it is possible for a release of gases to occur during a synthesis, e.g. due
to rupture of tubing in a module. Even if the material is in liquid phase, given the highventilation rate in the hot cells, the drops of liquid will be transported as an aerosol. This
class of incidents can be dealt with by using appropriate filters in the emission duct of each
hot cell. If the chemical form of the release makes the filtering approach ineffective, acompression station to collect the exhaust of the hot cell, activated if a predefined thresholdof radioactivity detected in the exhaust is exceeded, can be adopted (Mishani et al., 1999).
(137) In general, the main discharge point of the cyclotron and PET laboratories should beon the roof of the building complex, which may be some distance from the facility, requiringtens of metres of ducting.
(138) The radiological impact of any possible release of radioactive gas, in routine
operation or as a consequence of a malfunction in any phase of the process, must be assessed.
This requires the use of software codes developed under strict Quality Assurance andproperly validated, like HotSpot, released by the Lawrence Livermore National Laboratories(Homan and Aluzzi, 2020; Hotspot, 2022).
(139) The exhaust air travelling through the extraction system must be monitored before
release either through online monitoring or extraction of gas samples. The monitoring systemacts as an alarm system for detection of any unexpected discharges and can activate feedback
reactions, such as closure or regulation of the ventilation system. Furthermore, the monitoring
system will provide a record of routine gaseous releases, and can give the integrated amountof activity being released when properly calibrated (Marouli, 2007; de Sousa Lacerda et al.,2011).

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3.4. Radiation components of PET/CT imaging

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(140) When designing a PET/CT facility, there are two component radiations that need tobe considered that have very different shielding requirements. The 511 keV photons emission
resulting from positron annihilation and the x-ray emission associated with the accompanying
computed tomography (CT) scans. The emission component, aimed to study the in-vivo biodistribution of the radiopharmaceutical administered, is in general the reason for which theexamination is performed. The transmission CT component of the multi-modality scan may
have different goals: basically, it is necessary in order to ensure accurate attenuation
corrections for the emission component of the study, as well as to improve 'navigation' in the
anatomy of the patient, enabling regions of radiopharmaceutical uptake to be positioned moreaccurately. Furthermore, the CT component may be setup as a fully diagnostic study per se.
The purpose of the CT component will influence the radiation output level (Townsend,2008).
(141) The two radiation sources against which shielding is required will be consideredseparately, because there are fundamental differences both in the physical properties of theradiations and the sources of exposure. The 511 keV photons have a much higher energy than41

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other radiations used for imaging, so attenuation through photoelectric interaction is muchless. A rough indication of the differences can be obtained from comparison of values for thetenth value thicknesses (TVLs) radionuclide emissions with the thickness required toattenuate a beam of x rays. The TVL for 511 keV photons is of the order of 16 mm of lead,
whereas for the 140 keV gamma photons from 99mTc it is about 0.9 mm, but attenuation of
the wide range of lower energy photons in an x-ray beam is different, so 0.4 mm of lead
would reduce 120 kV CT x-ray air kerma by a factor of ten, 1.2 mm of lead would reduce it afactor of one hundred, and 2.1 mm by a factor of a thousand (Madsen et al., 2006; RPII,
2009; Smith and Stabin, 2012; Sutton et al, 2012).
(142) Exposure to 511 keV photons can occur during radiopharmaceutical preparation andinjection, and wherever staff is dealing with a patient after administration has taken place. In
particular, since several injected patients will be waiting for proper bio-distribution of theradiopharmaceutical before being admitted to the scanning room, waiting areas ('uptake
rooms') are typically those in which dose rates are higher. Therefore, not only is the design ofthe laboratory facilities important, but also the planning of the entire imaging process and theprogress of the patient, as the radiation source, through the department (Madsen et al., 2006;
IAEA, 2008b, 2010). Exposure to 511 keV photons will be almost continuous, but at a
relatively low dose rate. Instead, exposure to x rays will only occur in the scanning room
during the relatively short time (normally less than 1 min per PET/CT procedure) when the
CT scan is being performed, but the un-shielded dose rate levels from a CT scan are
significantly higher (up to 4–5 orders of magnitude in the direct beam) than those from apatient to whom a PET radiopharmaceutical has been administered.

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3.5. The journey of the PET patient through the facility

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(143) This section considers primarily requirements relating to imaging with 2-[18F]FDG
which are likely to make up the majority of the workload in most PET facilities (with PET,PET/CT, or PET/MR scanners). The following sections could be used a guidance for a
PET/MR, but specific consideration should be followed in relation to the MR component of
the study and its safety aspects.
(144) In summary, the patient examination with 2-[18F]FDG involves the following steps,
and an extensive description can be found, e.g. in EANM guidelines (Boellaard et al., 2015):• Written material about the procedure should be provided to the patient in due time
before the examination.
• The patient must fast for (at least) 4 hours before the injection, if the procedure is
performed for oncological purposes, to avoid an insulin mediated uptake in muscles
that either directly or by reducing the activity available could mask the malignity inquestion.
• The patient is received and again (orally) informed about the examination procedure,
and the patient's or caregiver's doubts and questions are answered.
• The patient is placed comfortably in a bed or an injection chair, and in a warm
environment, to avoid uptake of the radiopharmaceutical from brown fat, andinstructed to remain relaxed. Any muscle (or brain) activity shortly prior to tracer
injection may influence local uptake. In particular for brain examinations is thisimportant and here also visual and auditive stimulation should be avoided.
• An i.v. line is installed, to facilitate the administration of the radiopharmaceutical.

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• The amount of activity to be injected is determined according to local rules. Typically,a weight based activity is used.
• After injection, the patient remains resting so that the interval between 2-[18F]FDG
administration and the start of the PET acquisition becomes as scheduled, typically 60
minutes for oncological imaging. The i.v. line may be kept, in particular if CT contrast
is to be injected. The patient is asked to go to the toilet and empty their bladder before
being imaged. The patient is placed in the PET/CT and the examination is performed.
• Dynamic PET investigations require the administration of the radiopharmaceuticaldirectly on the scanner table, that depending on the protocol would be acquired
simultaneously with the start of the acquisition. In the case of PET/MR scanners, theadministration must be done taking care to use devices and shields compatible with themagnetic field.
• After the examination, the i.v. line is removed. The patient is instructed to drink
sufficient fluid and to empty their bladder frequently in order to minimise dose to thebladder wall.
• The patient is released, taking into account (local) rules relating to dose constraints tomembers of the public.

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(145) It is helpful to break down the journey of a 2-[18F]FDG patient through a department
into the component steps associated with different tasks. When patients are called forappointment, they will be given basic instructions, such as the need to fast for several hours,
and to avoid going to the PET facility with children or a pregnant woman.

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3.5.1. Checking the patient

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(146) Patients will be interviewed by a nuclear medicine physician or other qualified
healthcare professional. In many departments this detailed interview about the procedures
will be carried out at a separate appointment, but this may not necessarily be the case. This
step is a fundamental moment of exchange of information: the patient will provide
information about her/his condition, recent medication, interventions of concomitantpathologies and fasting conditions. This information could help in the interpretation of theimages.
(147) During the interview, or even better before the patient appointment, the correct
indication for PET (or other procedures) should be determined by a nuclear medicine
physician or a qualified specialist on the basis of clinical information provided by thereferring physician prior to the procedure.
(148) When patients attend for scanning their identification will be checked; this is a
critical point in the process as regards patient safety and radiological protection. Patient
identification is not a simple step, but rather a process that allows establishing correct
matching between a patient and appropriately intended interventions, as well as
communicating information about the patient’s identity accurately and reliably throughout
the continuum of care. Identification should be confirmed using more than one independent
identifier, e.g. name, ID number or social security number, date of birth, etc. At the sametime, she/he will be given an explanation of what the procedure involves, and on radiation
safety aspects. In some countries it could be requested for the patient to sign an informed
consent form. In the case of studies with 2-[18F]FDG a quick glucose testing will be
performed. This should all be performed prior to administration of radiopharmaceutical andthe patient should also be asked if she is pregnant or possibly pregnant, as well as if she is43

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breastfeeding. At this point the patient will be sent to the administration-uptake room whereradiopharmaceutical will be administered and the patient will remain at rest until the imaging
phase.

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3.5.2. Administering the radiopharmaceutical

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(149) To reduce the staff irradiation, and the movement of the patient, the administration
room should be the same as the uptake room. In most cases, this is one of a series of smallrooms, suitable for hosting a single patient. It is at the point the radiopharmaceutical has been
injected that the patient becomes a source of external radiation, and from then onwards
shielding of staff and others from the patient needs to be considered.
(150) It is essential not to inject the patient directly. Both for automatic injection systems
and in case of manual injection, it is suggested to place in advance an infusion line or cannulain the patient’s vein and pre-fill it with saline solution. Injection of the radiopharmaceutical
can be made once the operator is sure that the line is well positioned and open, connecting thesyringe to a three-way valve in the line, or injecting in a septa. This optimises the time ofoperation with the radioactive syringe and the distance to the patient, minimising the dose tostaff. In this way, injection using a shielded syringe becomes feasible and at the same time,
the possibility of extravasation is reduced.
(151) Exposure to PET radionuclides in the imaging department comes from vials orsyringes containing radiopharmaceutical activities for injection, as well as patients. However,vials of the batch of radiopharmaceutical, patient syringes etc. all have their local shielding.
The injection of the radiopharmaceutical is likely to be the largest component of the radiationdose received by clinical staff working in PET facilities (Heaton et al., 2014). If theradiopharmaceutical is drawn up from a multi-administration vial this can lead to significant
exposure, but automated dispensing systems, syringe fill stations, and specially designed
shielding are available commercially and careful consideration should be given to finding thebest option to suit the situation; further details are given in Section 8.
(152) Typical shielding of transport containers for vials of radiopharmaceuticals is ofabout 30–35 mm lead. Syringe shields are available in a variety of shapes and thicknesses;
the most frequently used are made in tungsten, with thicknesses of 2–10 mm, but also very
heavy shields are commercially available (tungsten, about 15 mm thick). Vials and syringes
can present a significant hazard to those manipulating them, but local shielding should ensurethat they do not contribute significantly to external dose rates within the main department,
and are not a major consideration in the design of shielding for the facility. The use of
syringe shields for administering PET radionuclides can reduce staff finger doses by 80%–90%. Although the shields need to be thick and the additional weight (up to 0.8 kg) can makeinjections difficult, they should always be used.
(153) Automatic patient injectors are available, that allow for installation of a vial of theradiopharmaceutical, as received by the production laboratory, and for automatic injection toa sequence of patients, by connecting single-use injection lines. These systems allow for a
reduction of the dose to the staff in the injection procedure (Lecchi et al., 2012; Schleipman
and Gerbaudo, 2012; Sánchez et al., 2015; Skovorodko et al., 2020) the critical aspect is theloading of the vial containing the batch of the radiopharmaceutical (of the order of 10 GBq oreven more). This operation may involve significant exposure of the operator; specificprocedures should be adopted and carefully monitored. Where these devices are used it may
be necessary to include structural reinforcement of work tops in order to take the weight of
the necessary shielding.
(154) Local procedures and staff expertise will determine the best approach. The use of
syringe-drawing devices and semi-automatic injectors can reduce finger doses by 80%–90%44DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

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and fully automatic dispensers can virtually eliminate hand exposure (Madsen et al., 2006;
Mattsson and Söderberg, 2011). The provision of equipment for drawing up of injections will
be discussed further in Section 8.

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3.5.3. The patient rest period

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(155) Once the radiopharmaceutical has been administered to the patient, the external dose
rates are significant (of the order of 30–50 μSv h−1 at 1 m, see in the following Section 3.6.4),
and so careful planning is required to maintain dose rates in the working environment at an
acceptable level, especially around the uptake rooms since it is where patients spend most of
their time other than on the scanner.
(156) Given the time needed to obtain optimal bio-distribution of the radiopharmaceutical(60–70 min for 2-[18F]FDG) versus the time of a scan with modern scanners (less than about
20 minutes, including patient access and positioning), there are likely to be a number ofpatients in a PET scanning facility at any one time during the working day either resting,
being cared for, or being scanned. It is recommended to have 3–4 individual shielded rooms /positions provided per PET/CT scanner. Furthermore, other patients will be waiting to bedischarged, or to receive information; a dedicated waiting area, different from the one usedprior to the study, should be provided.
(157) During the uptake period, patients should rest and avoid any exercise, as active
muscles will take up the radiopharmaceutical, and for brain studies minimise stimulation (noreading, talking, television, mobile phones etc.). Dim lights and soothing music can aid
relaxation and the temperature should be comfortable, as a cold environment has been known
to cause activation of brown adipose tissue leading to accumulation of 2-[18F]FDG that could
obscure metastatic disease (Cohade, 2010; Kiefer, 2017).
(158) The patient uptake rooms are the most relevant source of radiation exposure to staff
in a PET department. They should be positioned near the imaging room in order to facilitate
the transfer of patients, taking care, with their arrangement, distance and shielding, to avoid
unwanted dose levels in the control room and possible interference with the acquisition
equipment (IAEA, 2010). Closed circuit television cameras can be included in the uptake
rooms to allow staff to monitor patients remotely and allow audio communication without theneed for direct contact.

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3.5.4. The imaging period

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(159) The end of the uptake phase, when the radiopharmaceutical has been distributed
within the body, is the time for imaging. The patient should be requested to void their bladderin the toilet allocated specifically for active patients, and then move to the PET scanner room
(IAEA, 2010).
(160) Apart from the preparation and injection phase, the main period when staff will be
exposed is during the patient positioning and set-up of the scanner and assisting the patientfrom the scanning room when the scan has been completed. Staff should not need to be in thescanning room during the acquisition, although there is a possible exception, in the case ofsome (relatively rare) image guided biopsies or where blood samples are drawn for
quantification or research studies. The scan time used may vary to some extent, but with theuse of modern scanners, it can be reduced below 20 minutes.

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3.5.5. Patient discharge

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(161) When the acquisition of the PET procedure has finished, the patient should go to thechanging room and recover his/her clothes and possessions. At this time, the patient may
need to go to the toilet after the PET/CT study, or be required to as a protection measure, so
this should be taken into account when locating the toilet.
(162) A hot waiting area will be needed for some patients before leaving the facility while
their scans are checked, or for a post imaging interview with the staff. This room could also
be used to wait if a second/late image is needed.

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3.6. Design of a PET facility

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3.6.1. Planning the facility

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(163) The flow of all sources and incoming/outgoing materials should be carefully
considered in the design phase. Specific drawings illustrating the movement of each type ofmaterial, of staff, and of patients, should be prepared and optimised. Movement of patients
through the facility, and separating patients from staff not directly involved as much as
possible, are important considerations when setting out the design for a PET/CT suit.
(164) As for any other Nuclear Medicine facility, floors should have welded continuous
flooring in an impermeable material, washable and readily decontaminated, curved to thewalls, with all joints sealed. Walls should be finished in a smooth and washable surface.
Ceilings should be lined with acoustic tiles, washable or sprayed with a plastic washable
finish. Radiopharmacy laboratories should have a pharmaceutical grade ceiling (IAEA, 2018,2020a).
(165) Many different approaches can be taken to the design, which will depend on thelocal requirements such as the predicted workload and space available for the facility. The
numbers of patients scanned in a day varies considerably between facilities, but the aim isusually to maximise the number imaged, so it is common for all uptake rooms to be occupied
for most of the working day. The number of required resting bays will be determined mainlyby the time between patients, considering the uptake period and the duration of the PET/CT
acquisition. In general, not less than 3 or 4 individual uptake rooms are necessary per eachscanner (IAEA, 2008b, 2010).
(166) The flow of radiopharmaceuticals and the areas required will vary according to themethod of operation. There are several options and combinations regarding (1) how toreceive 2-[18F]FDG and other radiopharmaceuticals from an internal or externalRadiopharmacy, and (2) whether to use an automatic injector instead of manually injecting
the radiophamaceutical. The function, design, and capabilities of the dispensing/preparation
room would be different and must be accommodated to the working scenario.
(167) The room for radiopharmaceutical dispensing will normally be adjacent to theadministration-uptake rooms, and distances between these rooms, the active toilet, and thescan room should be kept as short as possible, to minimise patient movement.
(168) Distances from positions where staff and the public remain for longer times should
be maximised to take advantage of the inverse square law. The positions of the patient uptake
rooms should be as far as possible from the scanner control room, other offices, and any areas
where staff remain for long periods, but they should be close to the scanner room, to reducethe movement of patients within the working area. Areas adjacent to the administrationuptake rooms should have low occupancy where practicable. Lines of sight, between patient
administration-uptake rooms and positions where staff spend significant proportions of theirtime, should be avoided to reduce direct exposure from patient emissions. All criteria cannot

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be fulfilled, so any design will be a compromise based on the space available and the patient
workload.
(169) Administration-uptake rooms for individual patients should be of sufficient size toallow easy patient access and be able to take wheelchairs, trolleys or automatic injectors.
Bench space should be provided to take equipment such as syringe carriers and shields.
(170) Since patients are requested to void their bladder just before the beginning of theexamination, there should be a toilet designated solely for patients, adjacent to theuptake/resting area and wherever possible the patients should be able to use the toilet without
passing into the main corridor to avoid irradiating staff.
(171) In the administration area it is necessary to have an activity meter on hand to allow
checks to be made at the time of injection. A separate work surface will also be required forcompletion of clerical tasks. Benches, sinks, floors and other surfaces should all be easy todecontaminate. There should also be adequate storage room available for radioactive
materials, and radioactive waste, as well as general clinical consumables.
(172) The scanner room should have enough space for the movement of personnel with
their necessary tools, such as contrast media injector, anaesthesia trolley and others, aroundthe patient lying on the scanner bed. Extra space may be considered for a future replacementof the scanner.
(173) Adequate space is needed for sources used for calibration and daily QC of thescanners. Some models have linear sources installed in the gantry of the equipment, within ashielded container. Other models of scanner use external cylindrical or point sources. In mostcases these sources are of 68Ge/68Ga, but also 22Na or 137Cs are used. Typically, the range ofactivity of linear and cylindrical sources is in the range 20–80 MBq, while point sources havelower activities, but higher activities may be used for specialist applications, such as a highresolution research PET brain scanner that has a built in 137Cs source of 1.1 GBq fortransmission scanning. All of the sources are supplied by the vendor with their own shieldedcontainers. Some scanners may require additional space, a technical room, for the computers
and the cooling system.
(174) Consideration will need to be given to arrangements for the release of aqueous waste
to the sewer and a sink designated for this purpose, in addition to the sink for hand washing
which should be adjacent to the work area and have taps that can be operated without direct
hand contact. However, an additional waste water tank is not normally required. It is
important to ensure that “hot” sink and toilet plumbing discharge lines do not run under the
PET camera(s) and, if this is not avoidable, that sufficient shielding over the plumbing line isprovided to avoid interference with patient imaging (e.g. bolus of “hot” urine post uptake
period).
(175) Other hot areas of the facility are the temporary waste collection room, to allow thecontaminated materials to be safely collected and decay before disposal or any further step,and the decontamination room.
(176) Depending on the organisation of the hospital, reporting rooms for PET/CT, where
the images are checked when the examination is finished and where the medical report is
prepared, can be located in different positions. It is recommended to have at least a small
reporting room within the PET/CT facility as a workspace for nuclear medicine physicians, inorder to favour control of the workflow, capacity for solving current problems, decision
taking and timely communications with other staff. A wider reading/reporting room can also
be placed outside of the PET facility, or in a non-supervised area of the facility.

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3.6.2. Example of PET/CT facility design

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DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE(177) Fig. 3.1 shows a possible layout of a PET/CT facility. The drawing considers ahospital facility; therefore, inpatients may have access to the facility with a different entrance
than outpatients. The entry of the radiopharmaceutical from an internal/external
radiopharmacy has been considered through a sterile access system (SAS)/Pass-through inthe dispensing room, where the total activity received can be prepared according to the formof administration of the radiopharmaceutical, either by individual shielded syringes or with
an automatic injector.
(178) The waiting area is outside the supervised area of the facility. The patient entersfrom the left, after being accepted in the reception. The procedure can be explained to thepatient in the interview room, where they can be tested for glucose. The patient would enter
the controlled radiation section of the department, which makes up the centre and right-handpart of the plan. The radiopharmaceutical is to be administered in the patient administration
and uptake rooms.
(179) Patients clothes and belongings can be kept in the lockers until the end of theimaging procedure. In some cases it is preferred that the patients change their clothes prior toadministration of the radiopharmaceutical, to reduce the possibility of their clothes being
contaminated. In other situations, to optimise the patient flow, the next patient enters thechanging room adjacent to the scanner and can change his/her clothes, when the previous
patient is called inside the scanning room.
(180) After the injection the patient would wait in the shielded uptake rooms near to thescanning room. The number of uptake rooms will be determined partly by the workload andthe incorporation period of the radiopharmaceutical before the scan. The provision of four
administration-uptake rooms could allow the scanner to be used to maximum capacity.
Shielded walls in the uptake rooms may have angled tips, often called nibs or mini-mazes, torestrict any line-of-sight exposure of staff in the scanner control cubicle, in the corridor, andwhen assisting other patients in the other uptake rooms. Exposure of individual patients byradiation from other patients (regarded as a public exposure) is minimal, less than 50 µSv,
compared to the internal dose from the radiopharmaceutical (order of 5 mSv). The active
toilet is located within the administration-uptake room area, so that patients who use it do notpass along the main corridor, which would irradiate staff in the facility, and to reduce thepossibility from spread of patient related contamination (Kumar et al., 2015).

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Fig. 3.1. Schematic plan of the layout of a PET/CT facility. The patient route through the facility is
indicated by dotted line arrows. The diagram is not of a real facility and is not to scale.

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(181) The imaging room is in front of the administration-uptake rooms to optimise themovement of the patient. When the PET procedure is completed, the patient goes into thepatient changing room adjacent to the scanner, getting back his belongings. If necessary,
because a second/late image is needed or for a post imaging interview with the staff, thepatient can wait in a hot room before leaving the facility.

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3.6.3. 511 keV photon dose rates around PET patients

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(182) While patients are in the department, the activity within their bodies will decay as
the half-life of 18F is only 110 minutes and this can be taken into account in assessing doselevels. Decay during the rest period prior to the scan will reduce the activity administered byover 30%. The average dose rate over the rest period will be about 83% of the initial value.
The patient should be asked to use the toilet at the end of the rest period before the scan, and
it is estimated that this will reduce the activity by a further 15–20% (Madsen et al., 2006).
The amount of 2-[18F]FDG activity administered varies around the world, depending on
regional practice, patient cohort, diagnostic reference levels, and availability (Ducharme etal., 2009), being typically of about 300–370 MBq in Europe (EANM, 2016; ARSAC, 2021),
around 370–740 MBq in North America (SNMMI, 2018), and with median values of 220 and
257 MBq in Japan, depending on the origin (in-house-produced or delivered, respectively)(Abe et al., 2020). However, research and continuous developments in PET detectors andreconstruction algorithms, are increasing the sensitivity of scanners, and the values reported
here are likely to decrease in the future. The amount of activity administered will be a factor
in determining amounts of shielding required. Dose rates from unshielded sources and frompatients during the different phases reported in various publications are given in Table 3.1.

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3.6.4. Assessment of dose levels and protection requirements

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(183) When an initial layout has been developed, the flow and residence time of each typeof source can be evaluated for each area; inverse square law calculations should be used toassess potential dose rate levels from which shielding requirements can be determined. The
patients should be considered as radioactive sources and the times that active patients arelikely to be in the administration room, uptake rooms, and scanning rooms evaluated andcombined with appropriate dose rates (Table 3.1) to derive the doses resulting from eachsource. The workload in terms of the numbers of patients per week or per year is a crucial
factor in determining the dose levels and so the amount of protection.
(184) The patient administration area and uptake rooms will be a major source of
exposure. Therefore, they will need substantial shielding, as well as consideration of any
shine through paths from the patient couches that might irradiate others. Exposure frompatients in toilets will need to be considered, and is best done by evaluating the total amountof time that the toilet is likely to be occupied by active patients.
(185) Scanning of patients is likely to take place throughout the working day in order tomaximise throughput, so the scanning room will again require extensive shielding. This musttake account of both radiation emitted by the patient and the CT component of theexamination, and this is considered in more detail in Section 3.7.
(186) It is necessary at the outset to decide upon dose constraints that individuals within
the facility should not exceed during a year, relating to the annual dose limits. This will varywith country and region, as well as for individual roles. For staff working in the reception,
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adjacent offices, wards, or departments, a dose constraint applicable to a member of the
public, e.g. 300 µSv effective dose, representing 3/10th of a 1 mSv dose limit might beappropriate for staff not working directly with radiation, whereas for radiation workers ahigher constraint is likely to be required (IAEA, 2008b). The exposure of those in other areas
must be taken into account. Wherever possible offices and other rooms that are likely to beoccupied for a significant proportion of the time should not be sited adjacent to radiation
areas, and if this cannot be avoided, it will require the installation of additional shielding tominimise staff exposures.
Table 3.1. Dose rates from various sources of 18F exposure.

Source

Dose rate at 1 m(µGy h-1 MBq-1)

Dose rate at 1 mfrom 400 MBq(µGy h-1)Reference

Unshielded 18F source

0.148

59

Madsen et al., 2006

Unshielded 18F source

0.16

64

Delacroix et al.,
2002

Patient immediately after 18F
injection

0.092

37

Madsen et al., 2006

Patient immediately after 18F
injection

0.11

45–52

Benatar et al.,2000, Peet et al.,
2012

18

F uptake phase (average)

0.09

37

Benatar et al.,
2000*

18

F patient end of rest period

0.08

30

Benatar et al.,2000*
Lo Meo et al., 2014

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1967

*

18

F scan phase

0.06

24

Sutton et al., 201218

F patient leaving department

0.04

15

Cronin et al., 1999

Calculated from data in Benatar et al. (2000).

(187) The amount of exposure to staff working in different areas can be taken into accountby using occupancy factors (NCRP, 2004; Madsen et al., 2006; Sutton et al., 2012). Consider
the proportion of the time that staff will occupy in different locations within the department.
Areas such as the scanner control room, receptions areas, nurses’ stations and offices will beoccupied 100% of the time when the department is operational. Whereas there might only bepeople in staff rooms, wards, and clinics for 20% to 50% of the time, and corridors,
stairways, waiting rooms, and toilets might only be occupied for 5% to 15%. Whenconsidering occupancy of the corridor and the active toilet, this will apply to both staff andpatients. The derivation of protection requirements will be based on a comparison of theannual dose constraint with the annual doses within different parts of the facility.

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1969

3.7. Determination of shielding requirements for a PET/CT imaging
facility1970

3.7.1. Protection against PET annihilation photons

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(188) Once an initial layout for the facility has been devised and the positions andexposure times for radiopharmaceutical and patient sources have been determined, decisions
should be made about which walls require protection. Distances from all the source positions
to various rooms and locations where staff and others may be present should be determinedand dose levels calculated by application of the inverse square law to each source. Concreteor solid brick are suitable materials for shielding in terms of weight, although restrictions in
the available space and considerations on thermo-acoustical performance may make the useof lead preferable. A combination of concrete, or bricks, and lead is in several cases a goodtrade off. Lead protection will be required for the scanning room doors and lead loaded glass,or standard glass with very high thickness, is necessary for direct view windows. In general,use of shielding as close as possible to the sources, as in the case of uptake rooms, is more
effective. For some sources the radiation may pass through two or more protected walls, so
the shielding capabilities of each can then be summed during the calculation phase. For
example, in figure 3.1 radiation from patients in some of the uptake rooms will pass throughthe room shield and then the scanning room wall before reaching the scanner control cubicle.
Methods for determination of air kerma levels from PET scanning and calculating shielding
requirements are can be found in NCRP (2004), Madsen et al. (2006), IAEA (2008b), andSutton et al. (2012).
(189) When patient uptake rooms are provided with a door, a lead thickness of 2 mm ormore is required, but the trade-off between the protection and the ease of handling of the door
should be considered. In other cases, depending on the total space available, the presence of adoor may limit the access of patients in wheelchairs, trolleys, etc., and therefore use of
concrete barriers with angled tips (nibs or mini-mazes) may be preferred. Mobile leadbarriers with a thickness of 1 cm could help to improve shielding of the entrance of uptake
rooms, as well as to provide additional shielding during assistance to patients with specificneeds. A relatively low level of shielding from PET photons of patients is typically
acceptable for entrance doors in scanning rooms, since these doors are communicating withlow occupation areas, like corridors, if not with a patient changing room. A short concrete
barrier adjacent to a lead shielded door could be used to protect scanning room entrances
communicating with the control room. The eventual lower level of protection from PET 511
keV photons in doors makes it particularly important to minimise any lines of sight to areas
where staff are present for longer periods and sketching of isodose contours onto a plan of the
facility can aid in the optimisation process (Madsen et al., 2006; Peet et al., 2012).
(190) The exposure of staff and the public on floors above and below a PET facility needs
to be considered and additional shielding may be required to protect against PET radiation. If
the floor-to-floor distance is 4 m, then the distance to a person on the floor above can beconsidered as 4 m, but it will only be 3.5 m to a person standing on the floor below, as thesensitive organs are in the upper half of the body. The thickness of the floor slab issometimes sufficient to guarantee a certain absorption of photon radiation. However, often
either this thickness is made of a lighter material or pre-caste sections with a hollow core areused for structural reasons to optimise weight. Therefore, a careful investigation of the slab
structure may be necessary. In the case of a new construction, the concrete of density 2.3 g
cm-3 might be used, but the density and thickness are interdependent and can be adjusted
according to the protection requirements.

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2015
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(191) In determining the likely doses that individual staff members will receive forcomparison with dose constraints, it is necessary to take account of doses from preparation
and administration of radiopharmaceuticals, as well as dose rates from patients during
different phases, including periods of direct contact with patients that cannot be avoided. This
will be considered in detail in Section 8.

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3.7.2. PET/CT scanning room design and protection

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(192) The layout in the PET/CT scanning room should be designed to host patients in asafe environment during the examination, while streamlining workflow and patient
movement in order to ensure that the amount of time that staff spends handling and attending
patients is kept to a minimum. Space and distance are at a premium both to facilitate
operations and enable staff to maximise their distance from the patient as radiation source.
The entrance through which the patient is brought will normally be at the side or foot of thecouch, placement within the shadow of the scanner gantry may provide advantages in door
protection (see later). The control room would normally be to the front or side of the couch,with the scanner positioned at an acute angle to the walls to enable the nuclear medicine
technologist/radiographer to view the patient within the scanner gantry, and have sufficient
appreciation of the longitudinal position of the couch to enable a visual assessment to be
made. The distance from the CT scanner will determine the protection required for thecontrol cubicle window.
(193) Vendors of PET-CT scanner typically provide minimum and optimal spacerequirements for proper installation of the equipment, and suggest a layout. The project must
be approved by the designated persons, i.e. the responsible Physician and the Medical
Physicists/Radiation Protection Expert, as regards both the aspects of clinical operation andradiological protection. Shielding 511 keV photons in a broad beam geometry requires
specific calculations, taking into account multiple scatter and buildup beyond the walls.
Consolidated guidelines for shielding calculations are given in (Madsen et al., 2006; RPII,
2009; Sutton et al., 2012).
(194) Every facility will need to be considered on an individual basis and expert advice
taken from the healthcare and radiological protection professionals involved to maximise
patient, staff, and public safety, while providing an efficient workable arrangement. In larger
centres, scanning rooms can be located adjacent to each other and have a shared control areathat can provide advantages in communication and supervision. The control will containviewing windows for each scanner room, so care should be exercised in siting the windows,
to ensure that patients in one room are not able to view patients in the second.
(195) Given the difference in the HVL, the level of protection required for the higher
energy PET 511 keV photons is generally sufficient for protection of the walls of thescanning room against the heavily filtered x-ray beams with tube potentials of 120–140 kV
used for CT scans - the so called 'rule of the two sources' (NCRP, 2011). However, the doselevels in a scanning room from the CT component are significantly greater than those from a
PET patient. Approximate air kerma levels from various sources within the scanning roomfrom imaging of one patient are shown in Table 3.2.
(196) The presence of a window for direct viewing is always recommended. There can bedifferent approaches to protecting windows and doors against both 511 keV photons and CT
x rays. The x-ray dose per year in the control room can be reduced below 1 mSv with 2–3
mm of lead, but reducing the dose from 511 keV photons to this level will require thicker
shields. The control room window can be reduced in size to say 30 cm×40 cm, protected withlead glass equivalent to 4–5 mm lead at 511 keV, and additional vision provided throughcameras. Alternatively, the shielding requirement for the window can be based on achieving
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adequate protection of the control room from CT x rays, but accepting a certain dosetransmission from 511 keV photons and thus adapting the dose constraint for the limited area
in correspondence of the window. Shielding of the doors into the scanning room with lead
will reduce the exposure from x rays to an acceptable level and offer some protection against
511 keV photons. Decisions will depend on local approaches and requirements at each
installation.
(197) For the CT scanner, the primary beam is effectively attenuated by the scannerdetectors and hardware in the gantry, so the protection required is against scattered radiation
which is related to the amount of radiation incident on the skin of the patient. The scatter
dose distribution from a CT scanner is well defined and reproducible, because the x-ray tube
follows the same path around the patient for every rotation and all current models of PET-CT
scanner have the CT component in front, as the first element of the gantry. The PET detector
is heavily shielded, in order to avoid interference from activity in the body of the patient, outof the field of view. This shielding typically comprises several centimetres of tungsten, andits presence introduces a substantial amount of attenuation of the scattered dose due to the CTcomponent in the lateral and posterior directions (Fig. 3.2).
Table 3.2. Air kerma exposure during a single PET/CT scan from different component
sources to which staff might be exposed within the scanning room if there is no protection inplace.
Exposure scenario

Conditions
Distance frompatient

CT body scan DLP 600 mGy cm*
CT head scan DLP 600 mGy cm*
30 min scan period of PET patient(400 MBq) †Ceiling height
Scatter over 2 m barrier for CT
body scan 600 mGy cm*
*
†

2m

3m

217 µGy
84 µGy12–25 µGy

54 µGy21 µGy3–6 µGy

24 µGy10 µGy1.3–2.6 µGy

2m

3m

Distance frompatient

Scatter from wall into cubicle forCT body scan 600 mGy cm*

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1m

Unprotected 1.3 µGy
door

0.7 µGy

3.2 m

3.6 m

4.0 m

0.6 µGy

0.5 µGy

0.4 µGy

Scatter dose calculated using data from Sutton et al. (2012) and Martin (2015).
Results for dose rates from PET patients are variable (Tables 3.1 and 6.3), so a range of values is given here.

(198) The air kerma exposure within the control cubicle due to CT x-ray scatter fromadjacent walls, which might occur if the entrance into the scanning room is not shielded, aresimilar to those from direct exposure to radiation from the patient over the length of the scan
(Table 3.2). Therefore, in these circumstances it may be necessary to shield the door of the
PET/CT scanner control room with lead or use a mini-maze entrance, in order to protect
those inside from wall scatter, even if there is sufficient space to accommodate the operators
behind the main control barrier. This will also provide additional shielded space for otheroccupants. The likely dose level due to scatter from the ceiling slab into the control cubicle
and other adjacent areas, if the space above the protective screen and scanner room walls is

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not shielded, is about half that from direct exposure to the PET photons from the patient, so
extension of the protection to the ceiling slab, perhaps with a lower level of shielding above 2
m, may need to be considered (Sutton et al., 2012).
(199) The level of scatter can be predicted from the CT workload in terms of the doselength product (DLP) using scatter factors derived from measurements on a range of CT
scanners (NCRP, 2004; Wallace et al., 2011; Sutton et al 2012; Martin, 2015). The gantry
provides protection equivalent to about a factor of ten, so it may be possible to use lessshielding for doors and penetrations lying within the arc protected by the scanner gantry. It isuseful to consider the gantry position in regard to the location of large penetrations such as
ducts for air conditioning. Doors of the scanning room will require to be shielded typically by
about 2 mm of lead.
(200) Shielding may be required in floors and ceilings and should be assessed as for sidewalls (Madsen 2006). The protection of areas above and below the PET/CT scanning room
against PET 511 photons emissions is likely to be sufficient to protect against CT x rays.
Moreover, scattered x rays will only be incident on the floor and ceiling at an oblique angle,
because of attenuation by the gantry of vertical scatter), so an obliquity factor can be applied
to both the distance to the barrier and the barrier thickness in calculations (Sutton et al., 2012;
Martin, 2015).

Fig. 3.2. Example of dose in μGy/(1000 mAs) around one PET/CT system. Room is 8 m × 4.5 m(each field 0.5 m × 0.5 m).

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2118

4. IMAGING EQUIPMENT LIFE CYCLE

2119(201) Key points in this section:• The equipment life cycle is a well understood concept, and describes medical equipment,
including imaging equipment, from ‘cradle to grave’.
• The skills of each of the professionals involved should be respected in a team approach,using the methodology, expertise, and the process controls available for the optimal
management of equipment throughout its life cycle.
• The stages in the planning and creation of a PET/CT facility include justification,
specification, acquisition, installation, acceptance, commissioning, user training, before
the system is put into clinical use.
• The QA programme should comprise equipment performance evaluation during clinicaluse, and include QC measurements to verify that systems and components of the
PET/CT imaging system operate effectively and meets specifications. They should
include appropriate maintenance arrangements in place and require a system for ongoing
staff training after upgrades, periodic review of policies and procedures, and review ofdose misadministrations and near miss events.

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(202) The equipment life cycle is a well-known concept, and its application to imaging
equipment for x-ray installations has been described previously in Publication xxx on'Optimisation of radiological protection in digital radiology techniques for medical imaging'(ICRP, year1). This section reviews application of the principle for a PET/CT installation.

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4.1. The life cycle of equipment

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(203) PET facilities require a variety of equipment (IAEA, 2010; 2012), apart from
specific radiological protection equipment, such as dose and contamination monitors.
Facilities with the capacity for producing PET radionuclides will require a cyclotron andlaboratory areas for labelling of radiopharmaceuticals and quality control (QC), that would
include synthesis modules, radionuclide activity calibrators, and specific equipment for QC,
among others (IAEA, 2009a). The imaging area includes the scanner, currently in the form of
PET/CT or PET/MR, radionuclide activity calibrators, and radioactive verification sources.
(204) Setting up a new or replacing an existing PET facility requires careful planning by ateam of professionals (IAEA, 2010). Depending on the scope of the facility and the variety ofthe equipment, this team would include staff of the facility: nuclear medicine physicians,
nuclear medicine technologists/radiographer, medical physicists, radiopharmacists, andradiation safety experts.
(205) Medical imaging equipment is generally procured through a tender process whereinequipment suppliers are invited to submit a bid to supply the equipment or services. The teamneed to prepare a technical specification based on the clinical requirements, including
education and training, maintenance and repair arrangements. Once a contract has been
agreed, the equipment will be installed according to agreed standards, personnel trained in its
use, and a quality assurance (QA) programme put in place to ensure that standards aremaintained.
(206) The equipment life cycle applies to medical equipment from ‘cradle to grave’,equipment used both for production of radionuclides, their quality control and for imaging

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within the PET facility. But for simplicity, this section is focused on the lifecycle of theimaging part.
(207) The initial conception of the clinical need for the equipment must first be developed
into a proper robust justification. This is the embryo stage of the life-cycle shown at the topof Fig. 4.1. The skills of the different healthcare professionals, the methodology and expertiseavailable, and the process control to ensure required tasks are performed, all play a vital rolein understanding and managing equipment appropriately throughout its life and optimising
performance. The different aspects of the lifecycle of imaging equipment should beincorporated into a healthcare organisation’s planning and follow a systemic approachthrough acquisition, deployment, maintenance, QC, repair and disposal of imaging
equipment.

Fig. 4.1. The Life Cycle of PET imaging equipment, with a sub-cycle showing the requirements toensure performance is maintained during clinical use (ICRP, year1).

(208) Fig. 4.1 shows the elements required through the period leading up to the equipment
being put into clinical use, with a sub-cycle showing the requirements that are needed
continually to ensure performance is maintained and optimisation is improved. Steps
involved in acquiring the equipment, in enabling and installing of equipment, in theoperational requirements in clinical use, and the end of clinical use are described in thefollowing sections.
(209) The life cycle of the imaging equipment shown in Fig 4.1 can also be applied withsome degree of simplification to other equipment in the imaging part of the PET facility, likethe radiological protection elements (shielded protectors and radiation detectors) and sources
used for the verification of the PET scanner and the activity calibrators.

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4.2. Acquisition of equipment2188

4.2.1. Justification of equipment

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(210) The procurement of all medical imaging equipment should be justified, both in termsof clinical need and radiation dose. Justification should be evidence driven and take into
account present and future clinical applications and revisions of workflow, whilst ensuringthat there is no unnecessary proliferation of equipment. Justification of new or replacement
equipment requires the involvement of a multidisciplinary group (MG) composed of nuclear
medicine physicians, nuclear medicine technologists/radiographers, medical physicists,

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nurses or other health care professionals involved in the PET imaging procedures, andmanagement system leadership.

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4.2.2. The acquisition and procurement process

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(211) Once procurement of equipment has been justified, it is essential that a full
performance specification of the entire system is prepared to reduce the possibility of
inappropriate devices being purchased. This should include detail of the performance andregulatory requirements that the equipment will be expected to meet, and the manner (e.g.
procedures and technical documentation) in which the manufacturer/installer is expected todemonstrate that the equipment supplied meets the acceptance criteria (see Section 9.5.1).
The specification in first instance should define the clinical needs and, on this basis, theperformance parameters that are requested (e.g. depending on the most relevant use and otherequipment available). The specification should include maintenance requirements with
options for maintenance contracts and prices on essential spare parts and options, delivery
timescales, requirements on acceptance testing, commissioning, and the type and amount oftraining required.
(212) Specification is a task that requires input from all the members of the MG. The
specification document should:• address the issue of enabling and infrastructure work required – for example, what levelof connectivity is required for the equipment to function appropriately, and how thevendor will address those requirements within the organisation’s ICT infrastructure.
• include the resourcing and vendor activity involving the initial optimisation of equipment
to ensure that the purchase does not only include the technology and applications but
also the right initial setting of the technology for the first phase of optimisation inpractice. The initial optimisation would include specific PET protocols for the different
applications and radiopharmaceuticals, such as 2-[18F]FDG whole body oncologicalimaging, neurology, cardiology, paediatrics, with an indication of the optimal
administered activity for the established imaging time, and CT protocols according to thescan purposes (attenuation correction, anatomical positioning and full diagnostic).

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(213) A tender comprises the specification, and terms and conditions under which theequipment is to be purchased. Responses to the tender will form the basis for the evaluation
process, therefore questions posed by the specification document and stipulations regarding
terms and conditions should be correctly formulated. The vendor could be required to
identify options for the disposal of redundant equipment, and the removal of the verification
sources out of use.
(214) On receipt of tender returns the MG including procurement experts should convene
to consider the responses from the vendors offering their products. Evaluation should be
carried out in an objective manner against predetermined criteria to maintain not only
neutrality but to ensure selection of the optimal equipment package. After evaluation, lead intimes can be agreed, the contract signed, and the order placed. The contract should address allof the items included in the specification and the associated terms and conditions, including
the initial optimised protocol settings.

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4.3. Enabling and installation of equipment

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(215) Equipment life cycle is part of the facility life cycle. The operation of a PET facility
includes the scanner, and the management of radiopharmaceuticals and of sealed sources forequipment verification. According to international safety standards, the operation of a new
PET facility shall, unless notification alone is sufficient, apply to the regulatory body for
authorization, which shall take the form of either registration or licensing (IAEA, 2014b).
Any modification should require the submission to the regulatory body a notification and, as
appropriate, an application for authorization.
(216) Enabling and installation are essential components of the equipment life cycle.
Planning and construction of the PET facility rooms (see Section 3), protection, electrical andother services all need to be prepared beforehand. If the installation is not completed
correctly or the correct infrastructure and building work is not carried out appropriately thenat best delays will be encountered, but this may also lead to ongoing issues throughout thelife of the equipment. Basic connectivity issues and possible mitigation should be identified
at this stage as should issues around licensing and registration (WHO, 2019).

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4.3.1. Acceptance

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(217) Acceptance testing is the process whereby the purchasers satisfy themselves that theequipment supplier has provided what has been ordered, that it is safe to use, and that it
functions according to the manufacturer’s and purchaser’s specification. This will involve
both medical physicists and nuclear medicine technologists/radiographers, in consultation
with nuclear medicine physicians, and will include identifying the inventory and probably
performing electrical and mechanical safety checks. Regulatory requirements may requiredemonstration of radiation safety, which should be carried out at this stage. Acceptance tests
will involve quantitative measurements to demonstrate that the equipment specification interms of imaging performance is met. These tests should meet NEMA, IEC or other relevant
standards, but in some cases, they could be vendor-specific and follow the vendor’s
methodology. The set of QC tests should guarantee that the system parameters, modes andprogrammes are optimised for the intended clinical use and their deviations during theequipment life are within the acceptable limits.
(218) Acceptance tests for equipment in a PET, PET/CT, or PET/MR imaging facility aredescribed in Section 9. Sealed sources and phantoms with certain activities are required fortests of PET scanners and radionuclide activity calibrators, and information on this should be
included in the acceptance tests schedule. The presence of operator and service manuals
should be verified at this stage.

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4.3.2. Commissioning

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(219) In the commissioning phase, the purchaser should ensure that the equipment(including PET/CT or PET/MRI, radionuclide calibrator, radiation monitoring instruments…)
is ready and optimised for clinical use and establish baseline values against which the resultsof subsequent routine performance tests (constancy tests) can be made (see Section 9). Afterany major work on the equipment the relevant baseline test may have to be repeated; forexample, when the electronic components of a set of PET block detectors or the CT x-ray
tube are replaced.
(220) Clinical protocols, which include issues such as the amount of activity used, the time
between its administration and the acquisition of the images, and reconstruction protocols,
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equipment operated by the healthcare organisation. This could include the use of CT in thecontext of PET/CT protocols, and the harmonisation of PET image quality among scanners.
The accreditation of the PET/CT performance can be done by an international organisation(Aide, 2017). Commissioning should also address issues of interoperability in relation to thehospital imaging system (AAPM, 2019a).

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4.3.3. User training

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(221) User training on PET/CT or PET/MRI scanners, that may include nuclear medicine
specialist, radiologist, nuclear medicine technologist/radiographer, nurses, and medical
physicist, is critical for safe, optimised use of any imaging equipment (see Section 10).
Organisations should have a policy for user training that should be part of the Quality
Management Programme where it exists (see Section 9). Users need to understand theintended purpose and normal functioning of the device in order to use it effectively andsafely. Initial user training should ideally be provided by the representative of theinstaller/manufacturer (applications specialist) following acceptance and before theequipment is put into clinical use. Since all end users of the equipment may not be able toreceive this initial training, it is important that 'superusers' are identified who are given
sufficient training to allow them to disseminate the knowledge to others and provide practicalguidance for subsequent refinement of protocol optimisation. These superusers can be
encouraged to develop their knowledge and skills further and can then provide refresher
courses, training for new staff, and be involved in additional training required for updates. Alltraining should be recorded for quality, continuing professional development (CPD), andsafety purposes. User manual needs to be available in the local language for end user use
after user training is completed.

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4.4. Operational requirements for equipment in clinical use

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(222) A part of the overall QA programme is to optimise the equipment parameters, toensure the performance meets the specifications set during clinical use. Part of this isachieved through systematic QC, through which management facilitates measurement of theparameters used to test and verify that structures, systems, and components of the PET/CT or
PET/MRI imaging system are operating effectively and correspond to predetermined
requirements. The QC programme includes routine periodic (e.g. daily, weekly, monthly,quarterly, semi-annually etc.) testing to monitor technical performance (follow-up
measurements). Detailed tests of the equipment are described in Section 9. Each element of
the equipment life cycle contributes to successful optimisation and QC helps to ensure this isachieved through focussing attention on the many different aspects of performance that need
to be maintained.
(223) All medical imaging equipment must be maintained appropriately. Often equipment
comes with a limited warranty providing maintenance to manufacturers’ specifications for a
set time. Subsequent arrangements should be made using an evidence and risk-based
approach to decision making – costs alone should not be the determining factor. Decisions
about maintenance and contract management are often made by hospital stakeholders, andthose involved should have an understanding of the clinical implications of any decisions
made. Maintenance contracts should be specific and auditable and those personnel (in-houseor external) performing service and maintenance should be adequately trained and competentto operate the equipment they work with. When equipment is returned to clinical use fromeither planned preventative maintenance (PPM), scheduled in the maintenance contract, or
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repair, service personnel should provide an indication of what changes they have made andwhether those changes could impact on image quality or patient dose for CT. If a PPM or
repair has resulted in a potential change to image quality or dose, a predetermined QC test
should be performed by a qualified specialist according to the QA/QC programme.
(224) Upgrades occur throughout the life cycle of imaging equipment, and these should beunderstood both by users and nuclear medicine management. It is important that appropriate
commissioning tests are performed after an upgrade (software or hardware) and that staff
groups are properly trained in the changes.
(225) An adverse incident is an event that causes, or has the potential to cause, unexpectedor unwanted effects involving the safety of patients or other persons. The activities ofradionuclides involved in PET procedures should not produce deterministic effects inpatients, but staff finger doses may exceed dose limits if radiological protection measures are
not well managed, especially during radiopharmaceutical administration (see Section 8).
(226) In PET/CT and PET/MR, any misadministration of a radiopharmaceutical or otheroverexposure due to both PET and CT of a patient or a staff member, would count as a safetyissue, and above guidance levels would require to be reported to the regulator. However, it isalso useful to record and learn from near misses and Local Adverse Event Reviews should be
integral to the routine use of medical imaging equipment.

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4.5. The end of clinical use and equipment disposal

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(227) At some point during its life cycle, the equipment will become a candidate for
disposal. This may be for example, because it can no longer be repaired or be brought
economically back to acceptable specification by the manufacturer, it is no longer supportedby the manufacturer, a lease has expired, it is obsolete, its clinical performance is no longer
sufficient for the task, or repurposing is required. At that point, a decision to remove it fromservice might be made. However, a policy on removal from service is an essential part ofdevice management (MHRA, 2021) and planning for replacement should be in hand before
any decision is necessary. The planning cycle should include considerations on thejustification for the new equipment that is to be obtained and go on to consider all of theother items in the equipment life cycle identified above. The cycle should take into accountHealth Technology Assessments where they exist.
(228) Because of their diversity and complexity, there are many ways that medical devices
such as PET scanners or radionuclide activity calibrators can be disposed of. Options range
from resale for subsequent reuse to scrappage, where appropriate consideration ofenvironmental impact and relevant regulatory controls should be considered. When donation
is an option, potential health risks must be considered, and equipment safety and performance
should be verified prior to donation. Decommission procedures will need to be followed by
performing contamination survey to include areas surveys and area wipes to ensure noresidual radioactivity is present above background and this survey should be submitted to theRadiation Safety officer for review and signoff.
(229) According to the World Health Organisation (WHO), quality problems associatedwith donated medical devices have been reported in many countries. These problems often
result in receiving countries incurring unwanted costs for maintenance and disposal and may
also create the impression that the equipment is 'substandard' and has been 'dumped' on areceiving country (WHO, 2017). Specific advice on the donation of medical imaging
equipment can be found in WHO (2011) and THET (2013).
(230) Sealed radioactive sources used for the verification and calibration of PET scanners
and of the activity meters have to be replaced periodically because activity decay limits their
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proper use. Adequate disposal according to the national regulations should be followed. The
source should be treated as radioactive waste, and its management should follow basic
standards with the cooperation of the source supplier [see requirement 31 in 'Radiation
protection and safety of radiation sources: International basic safety standards' (IAEA,
2014b)]. Disposal or removal of cyclotron has to be considered carefully in order to comply
with local regulations (IAEA, 2020c) (see Section 3.2.1, Para. 102).

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5. JUSTIFICATION AND OPTIMISATION OF PET, PET/CT AND
PET/MRI(231) Key points in this section:• Justification of PET, PET/CT, and PET/MRI should be established by considering thecharacteristics of evolving imaging technologies, and especially by taking advantage ofthe unique hybrid imaging features with PET/CT and PET/MRI.
• Evidence on diagnostic accuracy and clinical value of PET, PET/CT, and PET/MRI is
increasingly endorsing appropriate use in clinical areas including oncology, neurology,
and cardiology.
• The application of PET, PET/CT, and PET/MRI to an individual patient should bejustified, which can be facilitated in clinical situations by following referral criteria or
appropriateness criteria that have been proposed by professional bodies.
• Radiological exposure of the patient should be part of justification as well as
optimisation for both PET pharmaceuticals and CT in PET/CT as a hybrid imaging,considering the image quality.

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5.1. Characteristics of PET, PET/CT, and PET/MRI in association withjustification

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(232) The technologies of PET, PET/CT, and PET/MRI have been making progresses.
Nowadays, PET/CT scanners have almost replaced dedicated PET scanners that are used onlyin special fields such as brain and breast imaging. A PET/CT scanner is a hybrid imaging
modality, incorporating the benefits of PET and CT, and provides anatomical, functional andmolecular information through fused images, which may give significant impacts on the
management of patients (IAEA, 2008b). A PET/CT may require radiation safety standards ofboth techniques in terms of principles of justification and optimisation when applied topatients (IAEA, 2008b; Alenezi and Soliman, 2015). The information obtained by PET/CT ismore accurate in evaluating patients with known or suspected malignancies than theinformation obtained from either PET or CT alone or the results obtained from PET and CT
separately but interpreted side by side (Delbeke et al., 2006; Boellaard et al., 2015). Recent
technological advances have made PET/MRI a reality in clinical practices, which provides
advantages of good soft tissue resolution on MRI and no CT radiation over PET/CT(Mannheim et al., 2018).
(233) Among PET pharmaceuticals that have been developed and supplied, 2-[18F]FDG isthe most frequently used PET pharmaceutical worldwide for patients with disorders including
neoplasms, cardiac diseases, brain diseases, infection and acute and chronic inflammatory
conditions including vasculitis, and therefore radiological protection issues covering PET and
PET/CT performed using 2-[18F]FDG will involve the main part of discussions (Delbeke etal., 2006; Boellaard et al., 2015; IAEA, 2023). With growing applications of 68Ga
somatostatin analogues for neuroendocrine tumour (Bozkurt et al., 2017; Sanli et al., 2018)
and 68Ga-PSMA ligands for prostate cancer (Fendler et al., 2017; Liu et al., 2018; SchmidtHegemann et al., 2019) as evolving PET techniques, issues specific to PET pharmaceuticals
should be incorporated in the entire radiological protection measures of PET/CT for mainly
patients but also for the staff members and the public. Justification for the staff members andthe public in PET/CT is based on a common platform with other areas of use of ionisingradiation (ICRP, 2007a,b).

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5.2. Justification of radiological practices

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(234) Justification of a radiological practice in medicine generally depends on a review ofthe benefits and disadvantages of the possible options, both radiological and non-radiologicalpractices. In the fundamental recommendations, three levels of justification of a radiologicalpractice have been proposed as follows (ICRP, 2007a,b). At the first level, the proper use ofradiation in medicine is accepted as doing more good than harm to society, and this generallevel of justification is taken for granted in the radiological protection in medicine. At thesecond level, a specified procedure with a specified objective is defined and justified.
Justification of a specific radiological procedure is a matter for national and international
professional and scientific bodies, in conjunction with national health and radiologicalprotection authorities and international organisations. National variations are to be expectedby considering national incidence of a disease and availability of effective treatments. At thethird level, the application of the procedure to an individual patient must be justified. Suchjustification should include checking that the required information is not already available.
The details of the proposed procedure and of alternative procedures, the characteristics of theindividual patient, the expected dose to the patient, and the information on previous andsubsequent examination or treatment are key issues that can help make decisions. At theindividual/patient level the argument to support the decision to expose the patient, should bethat, according to the available scientific evidence, the radiologic procedure results would
probably change the patient management. Referral criteria or appropriateness criteria often
serve as a decision-aiding tool (Jadvar et al., 2017; Canadian Association of Radiologists,
2022; ACR, 2022; European Association of Nuclear Medicine, 2022; Society of Nuclear
Medicine and Molecular Imaging, 2022).

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5.3. Justification of PET, PET/CT, and PET/MRI procedures

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(235) When justification of PET, PET/CT, and PET/MRI is discussed, justification of PET
may usually be incorporated in that of PET/CT or PET/MRI because both PET and CT or
MRI should be justified in procedures at the facilities by the medical specialists. Combined
PET/CT devices provide both the metabolic information from PET and the anatomic
information from CT in a single examination (Garcheva-Tsacheva, 2015). On the basis of thisadvantage, substantial amount of evidence is continuously being accumulated on the role of
PET/CT in the management of patients with various disorders (Delbeke et al., 2006;
Boellaard et al., 2015; IAEA, 2023). Such evidence on diagnostic accuracy and clinical value
is endorsing the second level justification processes of PET/CT as one of appropriate
modalities available in clinical imaging examinations. Thereafter, the application of PET/CT
to a specific individual patient should be justified, which involves justification at the thirdlevel. This may be facilitated in daily routine clinical situations by following referral criteria
or appropriateness criteria that have been crafted and proposed by professional bodies (Jadvar
et al., 2017; Canadian Association of Radiologists, 2022; American College of Radiology,
2022; European Association of Nuclear Medicine, 2022; Society of Nuclear Medicine andMolecular Imaging, 2022), which have been defining the expanding roles of PET/CT as thenewer treatments of patients come up. The referral for a PET/CT decided on tumour boards
and other multidisciplinary group meetings, in which professionals from nuclear medicine
and radiology are present, is a growing tendency in clinical practice, with a clear commitment
to the justification process at the third level. With regard to justification for PET/MRI, it may
guide clinical management comparably to PET/CT and improve disease detectability, andpatients may benefit from the reduced radiation (Martin et al., 2020).
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DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE(236) In the clinical practices, the second and third levels of justification are a common
part of the everyday operations of medical imaging departments. Justification in general isdelegated to a member of the imaging team specifically the nuclear medicine specialist or theradiological practitioner, but it is important to understand that the entire team contributes toboth the second and third levels to ensure that justification happens effectively and that goodcommunication through a team approach will produce the best method for success. Eachmember of the team including referring physician, nuclear medicine specialist, radiologicalpractitioner, technologist/radiographer in nuclear medicine, CT and/or MRI, nurse, andmedical physicist, can use their resources including evidence-based guideline, appropriate
use criteria, and departmental protocols to facilitate the process of justification. Such imaging
teams will use appropriate criteria and guidelines that have been developed with a strong
evidence base to build their protocols for each diagnosis or for specific disease processes,
each of which will be the responsibility of the lead radiological practitioner. While eachmember has a distinctive role; the nuclear medicine specialist or radiological practitioner isproviding the input to the clinical referral guidelines; the technologist/radiographer in nuclear
medicine, CT and/or MRI is providing image acquisition protocols of the relevant imaging
modality and the physicist is providing information on how to achieve the best image withthe lowest dose achievable to obtain a high-quality image with input from the medical staff
responsible for reading the image. Once this process happens, the discussion then must takeplace between the referring physician and the nuclear medicine specialist or radiologicalpractitioner to resolve the matter which may result in the request being modified to a more
appropriate procedure, the request being cancelled with the reasons documented in thepatient’s notes, or the examination continuing to be performed.
(237) Application of PET/CT and PET/MRI has been evolving from mere diagnostic
imaging to image-guided external-beam radiation therapy planning (Konert et al., 2015).
Beside justification issues themselves, optimisation through quality assurance processes inimage acquisition constitutes a key for good practice and radiological protection in PET/CT
and is inseparable from justification in clinical circumstances. Recommendations foradministered activities of PET pharmaceuticals are provided by academic societies(Boellaard et al., 2015; Fendler et al., 2017) (see Section 6). Radiological exposure of thepatient should be part of justification as well as optimisation for both PET pharmaceuticals
and CT in PET/CT as a hybrid imaging (Salvatori et al., 2019). Radiation dose to patients of
PET pharmaceuticals have been evaluated on the basis of techniques including biokinetic
models and biokinetic data (ICRP, 2015a).
(238) CT protocols (parameters including voltage, tube current, rotation time, slice
thickness, and pitch) for PET/CT studies should be deliberately chosen according to theobjective of the CT examination, i.e. attenuation/scatter correction, low dose anatomic
localisation or standard higher dose for diagnostic image interpretation (Boellaard et al.,2015), which leads to the broad range of radiation doses to patients. Justification for both
PET and CT must be decided by the medical practitioners at the PET facilities. Recently,
concerns have been arising on cumulative radiation doses of patients who undergo repeatedradiological examinations. Implementation of justification for PET/CT examinations andutilisation of dose reduction measures (see Section 6) are key issues in coping with the
cumulative doses in patients (Hosono et al., 2021). Only a few reports on the cumulative
doses with PET/CT examinations are available in the literature. There are scenarios where thepatient is booked for both a PET/CT scan and a diagnostic CT scan. In this case thediagnostic CT scan could be done in the PET/CT with dual purpose, for attenuation
correction and the clinical CT – net reduction of CT by one on some cases.
(239) In relation to the use of intravenous contrast, Zeman and Akin point out that forindividual tumours very limited comparative literature of PET with and without IV contrast
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material has clearly indicated a superior approach. However, studies have identified no added
clinical benefit of IV contrast material administration in some PET/CT indications (Yau etal., 2005; Chiaravalloti et al., 2014; Barai et al., 2020). Without a net clinical benefit to thepatient, performing a costlier study with increased risk, ranging from increased radiation doseto possible contrast reactions, is not fully justified. As the debate continues over the use of
intravenous contrast material for PET/CT, we must first and foremost keep the patient inmind and acknowledge that more is not always better (Zeman and Akin, 2022).

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(240) In optimisation of protection of the patient in diagnostic procedures, the same person
gets the benefit and suffers the risk, and individual restrictions on patient dose could becounterproductive to the medical purpose of the procedure. Therefore, individual dose
constraints are not relevant. In PET/CT, the dose to the patient is deliberately administered,using national or local benchmarks and cannot be reduced indefinitely without impairing theintended outcome; if the dose were too low it would not provide sufficiently good image
quality (ICRP 2007a).
(241) Therefore, the term ‘ALARA’ (as low as reasonably achievable) that is used inrelation to optimisation of protection for occupational and public exposure situations is not
appropriate when referring to medical uses of radiation, as it omits an important component,
namely the benefit that is derived by the patient from the exposure (ICRP, year2). As statedin Publication 120 ‘the entire concept [of optimisation applied to medical exposures] implies
keeping patient exposure to the minimum necessary to achieve the required medical objective(diagnostic or therapeutic)’ (ICRP, 2013). In diagnostic imaging, and consequently in
PET/CT, it means that the quality of images is adequate to obtain the information needed for
diagnosis. “Use of the abbreviation ‘ALARA’ alone and out of this context may be
misleading and raise unnecessary controversy” (ICRP, year2).
(242) Because it is not appropriate to apply dose limits or dose constraints, since such
limits could do more harm than good, DRLs are applied for a particular procedure and used
as an optimisation tool (ICRP 2007a). More information on DRLs and their application in
PET and PET/CT is provided in section 6.4 below.
(243) The key to optimization is “to perform the right test with the right dose on the rightpatient at the right time” and recognize that “the radiation dose delivery by any radiologic
procedure should not be a determining factor in the selection of the most appropriate test”(Fahey and Stabin, 2014). Once a procedure has been clinically justified, the protocol foreach individual patient has to be optimized, taking into consideration all factors involved,
mainly, related to the patient, the age, the body surface and the clinical condition. For thelatter, the main balance to influence the protocol is between the need and risks with sedation
versus diminishing the duration of the images acquisition, eventually at the expense of aslightly higher dose delivery, which might be acceptable in older and seriously ill patients,
with a shorter postexposure life expectancy. Regarding age, the main challenges are inchildren, due to their higher radiosensitivity and longer postexposure life expectancy, and all
aspects have to be optimized both for the radiopharmaceutical (activity administered) andspecific paediatric CT protocols (Parisi et al, 2017). As for the body surface, increasing
radiopharmaceutical activity might not be solution to have good diagnostic quality images inobese adults (Chang et al, 2011), and the optimized protocol might require longer acquisition
times for the PET component and higher dose delivery from the CT component. The main
responsibility of the members of an imaging team is to keep updated in order to continuously
optimize the protocols to be used in each specific patient, e.g., accompanying artificial
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intelligence developments into instrumentation and software’s (Zaharchuk and Davidzon,
2021).

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6. OPTIMISATION RELATED TO THE MEDICAL EXPOSURE OF
PATIENTS, CARERS/COMFORTERS, AND RESEARCHVOLUNTEERS(244) Key points in this section:• The total radiation dose from a PET/CT examination is the combined dose from the
PET radiopharmaceutical and from the CT.
• New PET, PET/CT, or PET/MRI hardware and software can optimise the radiologicalprotection reducing radiation dose while maintaining image quality.
• ICRP recommends constitution of national DRLs to optimise protection in the medical
exposure of patients for diagnostic and interventional procedures including PET and
PET/CT. DRL values are not static.
• Infants and children have a higher risk of cancer after radiation exposure, versus
adults. This patient population deserves special consideration relative to justificationand optimisation in the PET and the CT components of the procedure.

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(245) ICRP has issued a number of reports addressing the radiation dose to patients fromradiopharmaceuticals for diagnostic nuclear medicine procedures. The first report contained
results from calculations of organ absorbed dose and effective dose equivalent per unit
activity administered for some 120 radiopharmaceuticals in regular use at the time (ICRP,
1987). It also included the short-lived positron emitting radionuclides and related PET
pharmaceuticals. Over the years, ICRP has provided reports, amendments, and corrections(ICRP, 1998, 2008a, 2015a). These provide conversion factors for administered activity toabsorbed dose to organs (in mGy MBq-1) and effective dose (in mSv MBq-1) based on known
biokinetic model applied to reference phantoms of patients of different ages (1-, 5-, 10- and15-year-olds and adult) (Table 6.1). Publication 128 on 'Radiation dose to patients fromradiopharmaceuticals: a compendium of current information related to frequently used
substances' dealt with 19 PET radiopharmaceuticals labelled with positron emitters such as
11
C, 15O, 18F, 68Ga, 82Rb, and 124I (ICRP, 2015a). However, the effective doses forradiopharmaceuticals calculated according to the ICRP Publication 60 in Table 6.1 are underrevision and will soon be updated to the ICRP formalism defined in ICRP Publication 103.
(246) 2-[18F]FDG is the most commonly used PET radiopharmaceutical. It accumulates inorgans or tissues, such as the brain, the heart and various types of tumours. It is excreted
through the kidneys and the urinary bladder. The absorbed dose to organs and tissues of an
adult patient as well as the effective dose are shown in Table 6.2 (Kamp et al, 2023). An
administered activity of 300 MBq will result in an effective dose of 5.1 mSv.
(247) During a PET/CT examination, the patient is exposed to radiation from both theradiopharmaceutical and CT. The total radiation dose from a PET/CT examination is the
combined dose from PET radiopharmaceutical and from CT.
(248) The magnitude of the radiation dose to the patient from the CT examination depends
on several scan parameters such as tube voltage, tube current including modulation, rotation
time, slice collimation, pitch, total scan length, and position in the body (although this is notreflected in the CTDI or DLP surrogate measure). Radiation dose in CT is typically measured
by using a simple cylindrical phantom and expressed as a volume averaged CT dose index

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DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE(CTDI). Volume CTDI (CTDIvol) is the parameter for the average absorbed dose at a pointwith the scan volume for a particular scan protocol for a standardised phantom (IEC, 2002).
To better represent the overall energy delivered by a given scan protocol, the CTDIvol can be
integrated over the scan length to compute the dose-length product (DLP). Dose descriptors
such as CTDIvol and DLP are to be used for comparison against reference doses set for typical
CT examinations (EC, 2000; ICRP, 2017a).
(249) CT scan of the PET/CT examination can be carried out for three different purposes.
The protocol for CT scan can be selected for attenuation correction of the PET image, foranatomical localisation of the radiopharmaceutical within the patient or for diagnosis using
CT itself (see Table 6.3 for examples of published protocols and doses) (Akin et al., 2017).
For the purpose of attenuation correction or anatomical localisation, CT image quality is not
an important issue. So, low dose CT with the use of a low tube current (30–50 mAs) for
anatomical localisation results in an effective dose to the patient of 3–6 mSv. For attenuation
correction alone, a much lower mAs is possible, as shown in Table 6.3, resulting in a lower
effective dose. When the CT scan is performed as a full diagnostic CT, using contrast agentsand several scan cycles, the effective dose to the patient varies from 11 to 20 mSv dependingon the scan parameters used.
Table 6.1. Normalised effective doses for commonly used PET radiopharmaceuticals.
Effective dose per unit activity administered (mSv MBq−1)
Effective dose as defined in ICRP Publication 103
RadiopharmaceuticalAdult
15 years
10 years
5 years−2−2−2
18
1.7×10
2.0×10
2.9×10
4.4×10−22-[ F]FDG*
18
−2
−2
−2
[ F]choline†
1.1×101.2×10
1.8×10
2.6×10−2[124I]iodide‡
9.0×10−1
1.5
1.9×10+1
3.1

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1 year
7.6×10−2
4.6×10−1
5.5

Effective dose as defined in ICRP Publication 60 (excerpt from ICRP, 2015a)
RadiopharmaceuticalAdult
15 years
10 years
5 years
1 year[18F]FET§
1.6×10−2
2.1×10−2
3.1×10−2
4.7×10−2
8.2×10−2[18F]FDOPA¶
2.5×10−2
3.2×10−2
4.9×10−2
7.0×10−2
1.0×10−1
18
−2
−2
−2
−2
[ F]fluoride
1.7×10
2.0×10
3.3×10
5.6×101.1×10−1[18F]FLT**
1.5×10−2
1.9×10−2
2.9×10−2
4.6×10−2
8.8×10−2
11
−3
−3
−3
−3
[ C]acetate
3.5×10
4.3×10
6.5×109.9×10
1.8×10−2[11C]methionine
8.2×10−3
1.1×10−2
1.6×10−2
2.5×10−2
4.7×10−2
11
−3
−3
−3
−2
[ C]raclopride
5.0×10
6.4×109.8×10
1.5×10
3.0×10−2[15O]water
1.1×10−3
1.4×10−3
2.3×10−3
3.8×10−3
7.7×10−3[82Rb]RbCl
1.1×10−3
1.4×10−3
3.0×10−3
4.9×10−3
8.5×10−3

2-[18F]FDG model based on Kamp et al (2023).
[ F]choline based on Guissani et al (2012).
ǂ 124[ I]iodide for saturated thyroid, intravenous administration is based on ICRP Publication 137 (ICRP, 2017b).
§
O-(2-[18F]-fluorethyl)-L-tyrosine.
¶ 18[ F]-fluoro-L-DOPA.
**
30-deoxy-[18F]-30-fluorothymidine.
*† 18(250) In a study calculating doses for 429 paediatric 2-[18F]FDG PET/CT patients, a meaneffective dose of 6.4 (±1.8) mSv was found for the CT component of the PET/CT exam,using a scan technique for attenuation correction and localization, not for diagnostic purposes(Quinn, 2020). This value reinforces the need to develop, in paediatrics, optimisation anddose-reduction strategies.
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Table 6.2. Organ absorbed doses for 2-[18F]FDG (Kamp et. al., 2023).
OrgansAdrenals
Brain
BreastColon wall
Endosteum (bone surface)ET region
Gall bladder wall
Heart wall
KidneysLiver
Lung
Lymphatic nodes
MuscleOesophagus
Oral mucosa
Ovaries
Pancreas
Prostate
Salivary glands
Skin
Small intestine wall
SpleenStomach wall
TestesThymusThyroid
Urinary bladder wall
Uterus/cervix
Effective dose [mSv/MBq]

AdultsMale
Female1.4×10−2
1.6×10−2−2
3.0×10
3.3×10−2−3
7.6×10
9.7×10−3−2
1.2×10
1.5×10−2
1.0×10−2
1.2×10−2−3
7.6×108.5×10−3−2
1.1×10
1.3×10−2−2
6.5×10
8.4×10−2
2.0×10−2
2.3×10−2−2
1.5×10
1.8×10−2−2
1.3×10
1.7×10−2−2
1.3×10
1.4×10−2
8.3×10−3
1.0×10−2−2
1.5×10
1.7×10−2−3
8.8×109.9×10−3--2.4×10−2
1.6×10−2
1.8×10−2−2
2.7×10--7.8×10−3
9.7×10−3
6.3×10−3
7.7×10−3
1.3×10−2
1.7×10−2−2
1.4×10
1.7×10−2−2
1.2×10
1.3×10−2−3
8.6×10--−3
9.8×101.2×10−2−3
9.1×101.1×10−2−2
7.5×109.2×10−2--3.3×10−2
1.7×10−2

15 years
Male
Female1.2×10−2
1.3×10−2−2
3.5×10
3.8×10−2−3
9.2×10
1.0×10−2−2
1.5×10
1.4×10−2
1.6×10−2
1.6×10−2−2
2.0×10
2.0×10−2−2
1.1×10
1.4×10−2−2
8.3×109.1×10−2
2.2×10−2
2.4×10−2−2
1.7×10
2.0×10−2−2
1.3×10
1.4×10−2−2
1.2×101.2×10−2
9.7×10−3
1.0×10−2−2
1.6×10
1.6×10−2−2
2.0×10
2.0×10−2--3.8×10−2
1.7×10−2
1.9×10−2−2
3.1×10--2.1×10−2
1.9×10−2
8.0×10−3
8.6×10−3
1.3×10−2
1.3×10−2−2
1.4×10
1.6×10−2−2
1.1×10
1.3×10−2−2
1.9×10--−2
1.4×10
1.5×10−2−2
1.3×10
1.3×10−2−2
9.1×109.2×10−2--9.0×10−2
2.0×10−2

Absorbed dose in mGy/MBq
10 years
5 years
Male
FemaleMale
Female2.0×10−2
2.0×10−2
3.4×10−2
3.4×10−2−2−2−2
3.7×10
4.1×10
4.1×10
4.5×10−2−2−2−2
1.4×10
1.4×10
2.5×10
2.4×10−2−2−2−2
2.2×102.2×10
3.7×10
3.5×10−2
2.4×10−2
2.4×10−2
4.5×10−2
4.4×10−2−2−2−2
2.5×10
2.5×10
2.9×10
2.9×10−2−2−2−2
1.8×10
1.8×10
2.9×10
2.9×10−2−1−1−1
1.4×10
1.4×102.2×102.2×10−1
3.2×10−2
3.2×10−2
5.3×10−2
5.3×10−2−2−2−2
2.8×102.8×10
4.2×10
4.3×10−2−2−2−2
2.0×10
2.0×10
3.0×10
3.0×10−2−2−2−2
1.8×10
1.8×10
3.0×10
3.0×10−2
1.6×10−2
1.6×10−2
2.6×10−2
2.5×10−2−2−2−2
2.5×10
2.5×10
4.0×10
4.0×10−2−2−2−2
2.7×10
2.7×10
3.3×10
3.3×10−2−2--5.0×10--7.4×10−2
2.8×10−2
2.8×10−2
4.5×10−2
4.5×10−2−2−2
5.3×10--7.5×10--2.5×10−2
2.5×10−2
3.3×10−2
3.3×10−2
1.3×10−2
1.3×10−2
2.2×10−2
2.2×10−2
1.8×10−2
1.9×10−2
3.3×10−2
3.5×10−2−2−2−2
2.3×10
2.3×10
3.8×10
3.8×10−2−2−2−2
1.8×10
1.8×10
3.1×10
3.1×10−2−2−2
2.4×10--3.9×10--−2−2−2
2.2×102.2×10
3.6×10
3.6×10−2−2−2−2
1.9×10
1.8×10
3.2×10
3.2×10−2−1−1−1
1.5×10
1.5×10
1.9×10
1.9×10−1−1--1.3×10--8.7×10−2
2.9×10−2
4.4×10−2

69

1 yearMale
Female6.5×10−2
6.5×10−2−2
5.6×10
5.6×10−2−2
4.2×10
4.2×10−2−2
7.2×10
7.1×10−2
8.9×10−2
8.9×10−2−2
4.0×10
4.0×10−2−2
4.9×10
5.0×10−2−1
3.9×10
3.9×10−1
8.9×10−2
8.9×10−2−2
7.4×10
7.4×10−2−2
5.8×10
5.8×10−2−2
5.1×105.1×10−2
4.8×10−2
4.8×10−2−2
6.7×10
6.7×10−2−2
5.0×10
5.0×10−2--1.2×10−1
7.9×10−2
7.9×10−2−1
1.4×10--5.2×10−2
5.2×10−2
4.2×10−2
4.2×10−2
6.3×10−2
6.3×10−2−2
7.0×10
7.1×10−2−2
5.8×10
5.8×10−2−2
5.5×10--−2
7.0×10
7.0×10−2−2
5.4×10
5.3×10−2−1
2.7×10
2.7×10−1--3.3×10−1
7.6×10−2

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Table 6.3. Data from Image Wisely, regarding the CT component for a whole-bodyoncological PET/CT scan with 2-[18F]FDG (Akin et al., 2017).
CTDIvol
CT Effective dose
CT
mAs
(mGy)
(mSv)
Attenuation correction 5–10
0.3–1.0
0.5–1.0
Localisation
30–60
2–4
3–6
Diagnostic
110–200
8–14
11–20

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(251) Effective dose is a dose quantity that provides an approximate indicator of possible
risk (ICRP, 2021). Since effective dose is derived from standard phantoms, it should not be
used to assess risks of stochastic effects in retrospective situations for exposures in identified
individuals. It should also not be used in epidemiological evaluations of human exposure(ICRP, 2007b).
(252) Use of the value for effective dose should be sufficient to give an indication of risk
compared to other medical procedures or other sources of radiation. But if a full assessmentof the risk for an individual is required, then this is best evaluated using appropriate risk
values for the individual tissues at risk, and for the age and gender distribution of the
population groups undergoing the medical procedures. For the exposure of young children,
since the risk would be higher, dose optimisation is more important.

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(253) There are several strategies that can be used to minimise the radiation dose to thepatient undergoing a PET, PET/CT, or PET/MRI scan. To ensure that the administration
activity injected to the patient is correct, it must be adequately measured using an activity
meter, ideally double-checked by a second person, and the activity meter should be calibrated
regularly. A thorough development of referral guidelines, a team culture, standard protocols
for common imaging procedures, and policies for quality assurance contributes to prevent
unnecessary radiation exposures and thus also to dose reduction (Alenezi et al, 2015).
(254) For the PET component, the best way to reduce dose is by reducing the injected
activity, since the dose is proportional to the administered activity. Reduction of PET tracer
dose might have an impact not only for the patient but also in the exposure of the nuclear
medicine staff. However, reducing the injected activity would result in a reduction in image
quality. One method of reducing the injected activity while maintaining image quality is byincreasing scan duration. However, this would come at the cost of decreased scanner
throughput as well as increased patient motion which leads to increased image blur (Devine
and Mawlawi, 2010).
(255) The patient should be encouraged to drink water and then void prior to scanning, todecrease the whole-body dose, especially the dose to the bladder. Since 2-[18F]FDG is mainly
excreted by the urinary system, the urinary bladder wall is the tissue that gets the highest
absorbed dose, 39 mGy for 300 MBq. This dose can be markedly reduced by encouraging thepatients to increase their consumption of water and frequently void their bladder (Boellaard etal., 2015).
(256) For the CT component, several acquisition parameters can be modified. Reduction involtage and/or current time product reduce radiation dose, but image quality become
degraded by increasing noise. If a diagnostic contrast-enhanced CT is needed, it is preferable
to perform a diagnostic CT only for limited portions of the body. For the rest of the body, alow-dose CT is sufficient for attenuation correction and anatomic localisation. If a full
diagnostic CT is needed, it could also be used for attenuation correction of the PET image
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and there is no need to make an additional low-dose CT in connection with the investigation.
However, for a diagnostic CT with contrast, it should be noticed that artefacts can appear if
no proper software that corrects them is used (IAEA, 2014a). If the patient has recently
undergone a clinically relevant CT examination there is no need to repeat it and only lowdose CT should be used. Using a low dose CT should also be considered in repeated PET
scan to have a better signal to background ratio for a limited part of the body, repeated PET
with another tracer (e.g. 11C-methionine + 2-[18F]FDG) and clinical trials with frequent
PET/CT scans. In this way the CT dose component can be reduced with a factor of 2-3(Mattsson et al., 2015). Another strategy that might be implemented in clinical activity is touse, for attenuation correction, an ultra-low dose CT. Prieto et al. (2021), through phantom
experiments, demonstrated that these ultra-low dose CT do not introduce noticeable
degradation in the attenuation corrected PET/CT.
(257) In PET/CT scans with different scan lengths, effective patient dose from PET is thesame and related to administered radiotracer activity. However, effective dose from CT
increases according to the scanned length. As demonstrated by Martí-Climent et al, the CT
effective doses were 8.0, 10.4, and 11.9 mSv for head and neck, torso, and whole-bodyprotocols, with mean scanned patient length of 761, 839, and 926 mm, respectively (MartíCliment et al., 2017).
(258) Prieto et al. (2018) reported that significant dose reduction is feasible in 2-[18F]FDG
PET/CT protocols without compromising diagnostic quality. 2-[18F]FDG activity was
reduced from 5.18 MBq/kg to 4.44 and 3.70 and reference CT current-time-product was
reduced from 120 mAs to 100 and 80. Effective dose from 2-[18F]FDG was gradually
reduced from 6.5 ± 1.4 to 5.7 ± 1.3 and 5.0 ± 1.0 mSv. Effective dose from CT was
progressively reduced from 9.5 ± 2.8 to 8.0 ± 2.3 and 6.2 ± 1.5 mSv. Overall, a significant
radiation dose reduction of 28.7% was reached. Despite a slight reduction in image quality,
the new regime was successfully implemented with readers reporting unchanged clinicalconfidence.
(259) In some clinical scenarios and if available, it could be considered using PET/MR
instead of PET/CT, thus reducing patient dose by omitting the CT exposure.

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(260) New PET, PET/CT, or PET/MRI hardware and software provide new opportunities
for radiological protection optimisation, reducing radiation dose while maintaining image
quality. Optimisation of protocols can be found in publications as well as in websites ofscientific educational initiatives, like Image Wisely (2023) and Image Gently Alliance(2023).
(261) Maintaining the image quality while still reducing the injected dose can be achievedby improving the scanner sensitivity. This can be achieved by scanning in 3D rather than 2D
mode, by increasing the axial extent of the scanner, or, most recently, by acquiring PET data
in TOF mode. According to a nation-wide questionnaire in Korea, the radiation doses from 2[18F]FDG and CT were significantly lower in case of newer scanners than older ones (6.10 to
4.60 MBq/kg; P < 0.001) (Kwon et al., 2016). Advanced PET technologies such as TOF
acquisition and PSF recovery were also related to low radiation dose (P < 0.001).
(262) Regarding 2-[18F]FDG, the EANM recommends using administered activities of 380
MBq for 2D and 190 MBq for 3D for a standard adult patient (75 ± 5 kg) (Boellaard et al.,2015). The EANM guideline recommends the minimum 2-[18F]FDG administered activities
in adults, which assume a linear or a quadratic relationship between PET acquisition time per
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bed position, patient weight and recommended 2-[18F]FDG activity. Compared with thelinear activity prescription, the quadratic scheme results in a slightly higher administeredactivity for patients >75 kg. This compensates degradation of image quality due to the lower
signal to noise ratio from excessive attenuation. One may decide to apply a higher activity
and reduce the duration of the study. However, it is preferable to use a reduced activity andincrease the study duration, keeping ALARA principles in mind. For patients weighing over
90 kg, increasing the emission acquisition time per bed position is recommended rather thanincreasing the administered 2-[18F]FDG activity by the quadratic scheme.
(263) Newer PET, PET/CT, or PET/MRI scanners with TOF technology improve image
contrast and higher sensitivity, which can help to overcome poor signal from large patients.
Use of TOF technology permits a decrease in the average administered activity of ~25%
(from 4.6 MBq kg-1 to 3.5 MBq kg-1) without loss of image quality (Etard et al., 2012).
(264) Increasing axial field of view of the scanner is increasing sensitivity of PET signal
from the patients in 3D mode. Recently, the total body PET system covering total body wasdeveloped. The 195 cm axial field of view of the EXPLORER PET/CT scanner is sufficient
to cover the entire human adult body in a single acquisition (Cherry, et al., 2018). Injection of
8.3 MBq 2-[18F]FDG is sufficient to acquire PET images in 10 min. This corresponds to aneffective dose of 0.16 mSv (Badawi et al., 2019).
(265) Several CT radiation dose quality assurance tools are available. The CT radiationdose can be lowered by adjusting a combination of the following parameters: shorter scan
length, lower tube current (i.e. mAs), lower tube voltage (i.e, kVp), automatic tube current
modulation and properly centring the patient, collimation, increase pitch, image acquisitionand processing software options such as iterative reconstruction and thicker slice thickness.
(McCollough et al., 2006; Huang et al., 2009; Singh et al., 2011; Martin and Sookpeng, 2016;
ICRP, year2).
(266) Using optimal reconstruction parameters helps to obtain better diagnostic image
quality with less radiation dose. Image reconstruction techniques such as iterative
reconstruction, while requiring more computation, have many advantages over filtered backprojection (FBP). A study by Shin et al. (2013) reported that, in abdominal CT, throughapplying new iterative reconstruction algorithms, and an automated kV modulation, the dose
was reduced by 41.3%, while maintaining the same image noise as in the standard-dose FBP
images.
(267) Park et al. (2018) proposed a deep-learning-based approach for CT image superresolution. The convolutional neural network yielded high-resolution images (thin slice) once
the low-resolution image (thick slice) was given. Thus, artificial intelligence using deeplearning feature may help to reduce radiation dose in CT. Recently, some manufacturers haveintroduced deep learning reconstruction algorithms into their scanners, which not only lowers
radiation dose, but also improves image quality and speeds reconstruction, being presently
considered the future of CT (McLeavy et al., 2021).

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6.4. The value of DRLs for optimisation of PET and PET/CT

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2781

(268) ICRP recommends the constitution of national DRLs to optimise protection in the
medical exposure of patients for diagnostic and interventional procedures (ICRP, 2017a). In
Europe, this is also mandated to member states through Council Directives, the last being
Council Directive 2013/59/EURATOM (Council of The European Union, 2013). DRLs aredefined as dose levels in radiological diagnostic and interventional procedures or typicallevels of radiopharmaceutical activity for groups of standard-sized patients or standard
phantom.
72

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2793
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2799
2800
2801
2802
2803
2804
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2806
2807
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2809
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2812
2813
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DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE(269) A DRL value is a selected level of a radiation dose quantity for broadly defined
types of equipment for typical examinations for groups of patients within an agreed weight
range or, in certain specific circumstances, a standard phantom. Radiation dose quantities
used for DRLs should be appropriate to the imaging modality being evaluated, should assess
the amount of ionising radiation applied to perform a medical imaging task, and should be
easily measured or determined. When two imaging modalities are used for the sameprocedure such as PET/CT, it is appropriate to set and present DRLs for both modalities
independently.
(270) DRLs are derived from an arbitrary threshold from a distribution of values obtained
locally and collected nationally or regionally. Data for determining national DRL values are
obtained from surveys. Values of appropriate dose quantities from patient examinations arecollected from several different health facilities. The 75th percentile value of the distributionof median values (the 50th percentile) of a dose quantity at healthcare facilities throughout acountry is used as the national DRL.
(271) Median values of distributions of dose quantities at a facility should be comparedwith DRL values. If a DRL value for any procedure is exceeded, an investigation should beundertaken without undue delay to determine possible reasons, and if it is shown that
corrective action is required, a plan should be implemented and documented. A dose below a
DRL value does not, by itself, indicate that the procedure is performed at an optimised level
regarding the amount of radiation used. Image quality is always to be considered in
optimisation. The median dose may be considered as a balance point of image quality anddose in the general review. Users who have values significantly lower than the median of thenational or regional distribution may need to look at image quality as a priority.
(272) Where it is apparent that further optimisation is being achieved locally, or where nonational DRL values exist, ‘local DRLs or typical values’ based on audits or surveys might
be introduced to further assist the optimisation process.
(273) Values of DRL quantities for individual patients should not be compared withnational or regional DRL values, because the DRL process is intended for optimisation ofprotection for groups of patients, and is based on standard patients, not individual patients.
National or regional DRL values should not be used as dose limits. Dose limits do not apply
to medical exposures of patients.
(274) DRL values are not static. As optimisation of examinations continues or hardware
and software improve, DRLs should be updated on a regular basis. The DRL process should
be applied in a continual process of quality assurance (QA), with repeat surveys following
any optimisation, and then repetition of the whole process after an appropriate time interval.
National and regional DRLs should be revised at regular intervals of 3–5 years, or more
frequently when substantial changes in technology, new imaging protocols or improved postprocessing of images become available.
(275) For nuclear medicine, DRL quantities will be established in terms of theadministered activity. The ideal is for the administered activity to be adjusted for patient
weight. For some procedures, activity per kg body weight of a specific radionuclide for a
specific clinical task and the radiopharmaceutical used may be appropriate. Different
radiopharmaceuticals may be used for PET imaging, depending on the clinical condition andthe purpose of the study. Since the physical half-lives of radionuclides and biological halftimes of radiopharmaceuticals are different, DRL values should be set for eachradiopharmaceutical. DRL also depends on the diagnostic purpose. The administered 2[18F]FDG activity is different for whole body oncological or brain studies (Martí-Climent etal., 2017). Administration of Radioactive Substances Advisory Committee (ARSAC)
published DRLs, effective doses and dose to uterus of commonly used PET procedures fromUK in Notes for Guidance on the Clinical Administration of radiopharmaceuticals and Use of
73

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Sealed Radioactive Sources (ARSAC, 2021) (Table 6.4). The effective doses given in these
Notes have been calculated from the corresponding DRL using the methodology described in
Publication 128 (ICRP, 2015a), using weighting factors from Publication 60 (ICRP, 1991).
DRLs are varying among countries and regions (Table 6.5) (Song et al., 2019).
(276) For CT imaging in PET/CT, volume CT dose index (CTDIvol) and dose-length
product (DLP) are used for DRL quantities which are displayed from the CT scanners.
Patient dose depends on the purpose of the CT examination. DRL values for diagnostic CT ofthe trunk are too high for the CT component of PET/CT if the CT is performed only forattenuation correction and localisation. Despite wide variations between PET/CT protocols(4-fold variations in CTDIvol), CT DRL values of 8 mGy (CTDIvol) and 750 mGy⋅cm (DLP)
for attenuation correction and localisation have been proposed for whole-body PET/CT in
France (Etard et al., 2012). Since there is a wide variation of dose depending on the purposeof CT scan, separate DRLs for attenuation correction, localisation and diagnostic scansshould be proposed.

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Table 6.4. DRLs, effective doses (ED) and dose to uterus of PET procedures (ARSAC, 2021).
Radionuclide Chemical form
(MBq kg−1)[11C]choline[11C]choline[11C]methionine[13N]ammonia[18F]choline
2-[18F]FDG[18F]florbetaben[18F]florbetapir[18F]fluoride[18F]FET
6-[18F]F-DOPA[18F]flutemetamol[68Ga]Ga -DOTATATE /DOTATOC / DOTANOC

2847[68Ga]Ga -PSMA[82Rb]RbCl
IV, Intravenous.

Investigation
hepatocellular cancer imaging
prostate cancer imaging
brain tumour imaging
parathyroid tumour imaging
myocardial imaging
hepatocellular cancer imaging
prostate cancer imaging
brain tumour imaging
differential diagnosis of dementia
focal epilepsy
infection/inflammation imaging
myocardial imaging
whole body tumour imaging
cerebral amyloid assessment
cerebral amyloid assessmentbone imaging
brain tumour imaging
neuroendocrine tumour imaging
suspected congenital hyperinsulinism
cerebral amyloid assessment
somatostatin receptor imaging

Routeof admin
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV
IV

DRL
(MBq)
370
370
400
740
550
370
370
250
250
250
400
400
400
300
370
250
370
280
280
185
250

Prostate cancer imaging
Myocardial imaging

IV
IV

200
2220

75

Activity by
Weight(MBq Kg−1)

4
4

4.5
4.5

4
4

ED
(mSv)
1.6
1.6
3.3
6.1
2
7.4
7.4
4.8
4.8
4.8
7.6
7.6
7.6
5.8
6.9
4.3
5.9
7
7
5.9
6.4 TATE
4.2 NOC5.8 TOC
4.6
2.4

Dose touterus
(mGy)
0.7
n/a
2.7
5
1.4
5.6
n/a
4.5
4.5
4.5
7.2
7.2
7.2
4.9
5.8
3.3
6.3
7.8
7.8
4.6
3.7
n/a
2.2

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Table 6.5. Diagnostic reference levels of 2-[18F]FDG PET procedures among different
countries and regions (MBq) (Song et al., 2019).
Procedures
NCRP
EU
UK
Australia Brazil
Japan
Korea
2-[18F]FDG
461–710 200–400 400
310
370
240
370
(tumour)2-[18F]FDG (brain)
250
250
350
240
370

2850
2851

NCRP, National Council on Radiation Protection and Measurements; EU, European Union; UK, United
Kingdom.

2852

6.5. Radiological protection and dose issues in paediatric patients

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(277) Infants and children have more risk of cancer than adults after radiation exposure
since not only are their organs and tissues more sensitive to radiation, but also, they have alonger post exposure life expectancy. Thus, it is prudent for those using the technology tounderstand the factors that affect radiation dose from both the PET and the CT components ofthe procedure (Fahey, 2009).
(278) Using effective dose, which averages risk in both sexes and over wide age ranges, is
not ideal for estimating paediatric radiation risk. Thus, there are limitations of using effective
dose for comparing the radiation risk of one age group to another group. Despite these
constraints, effective dose remains most useful as a method for comparing the potential
radiation effects of different medical imaging studies to children within a single age group.
(279) Calculation of organ-absorbed doses relies on biokinetic models for each organ andeach radiopharmaceutical. The ICRP typically uses the same biokinetic models for all ages,
as most data are from adults, with little paediatric-specific biokinetic data. In somecircumstances, this may overestimate dose, as children may have more rapid clearance ofradiopharmaceuticals (ICRP, 2015a).
(280) For children and adolescents, administered 2-[18F]FDG activity should adhere to themost recent EANM or Society of Nuclear Medicine and Molecular Imaging (SNMMI)
recommendations on paediatric radiopharmaceutical administration (Treves, 2016; EANM,
2016) or national activity limits, if national limits are lower. Fahey F.H. et al demonstrated
that for commonly performed paediatric nuclear medicine studies, following either the
EANM Dosage Card (version 1.5.2008) (Lassmann et al., 2008) or the 2010 North American
consensus guidelines for administered activities of radiopharmaceuticals (Gelfand et al.,2011) can result in substantial differences in radiation exposure for the same procedure(Fahey et al., 2016). This discordance has identified opportunities for harmonization of theguidelines, which may lead to further reduction in nuclear medicine radiation doses inchildren (Table 6.6) (Lassmann and Treves, 2014, Treves and Lassmann, 2014; Grant et al.,2015). EANM Dosage Card set the minimum values determined based upon considerations
concerning the limitations of PET scanners in terms of image quality. However, PET imagesof sufficient quality can be obtained with an activity that is considerably less than thatsuggested as the 'minimum' in the new dosage card, considering the overall gain in truecoincidences in a small body (Holm et al., 2007). Also, the administered activity might be
reduced especially when using newer PET systems, provided that these optimised protocols
guarantee high-quality studies (Vali et al, 2021).
(281) Recently, IAEA conducted a survey on paediatric nuclear medicine practice, inwhich 133 institutes from 62 different IAEA member states participated. For 2-[18F]FDG
PET more than half of the facilities reported to use the EANM Paediatric Dosage Card, andthe level of compliance found for this exam was high, with not more than 4% of the institutes
exceeding 120% of the EANM recommended activity. Also, most of the facilities (more than
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DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

90%) stated that they were using tube current modulation in children, for their CT
acquisitions (Poli et al., 2020). Another survey, aimed at evaluating the impact of the 2010
North American Consensus Guidelines, was undertaken in the United States in the Spring of2013 and gathered information from 121 sites. Thirteen out of the 18 sites that performed
paediatric studies with 2-[18F]FDG, reported that they were familiar with the Guidelines and84,6% responded that their administered activities were +20% the recommended value of theguideline (Fahey et al., 2016).
Table 6.6. Radiation dose estimates for 2-[18F]FDG PET for adults and children at four
different ages using the administered activities recommended by the European Association of
Nuclear Medicine Dosage Card (EANM, 2016) and the 2010 North American (NA)consensus guidelines (Grant et al., 2015).
Age
1 year
5 years 10 years 15 years Adult
Nominal weight (kg)
9.8
19
32
55
70
18
2-[ F]FDG PET torso
EANM administered activity (MBq)
70
120
189
302
370
EANM effective dose (mSv)
6.7
6.7
7.0
7.2
7.0
NA administered activity (5.2 MBq kg−1) 51
99
166
286
364
NA effective dose (mSv)
4.8
5.5
6.2
6.9
6.9
NA critical organ dose (mGy) - Bladder 24
34
42
46
47
2-[18F]FDG PET brain
EANM administered activity (MBq)
37
65
102
163
200
EANM effective dose (mSv)
3.3
3.4
3.8
3.9
3.8
−1
NA administered activity (3.7 MBq kg ) 37
70
118
204
259
NA effective dose (mSv)
3.5
3.9
4.4
4.9
4.9
NA critical organ dose (mGy) - Bladder 17
24
30
33
34
(282) There are several strategies for decreasing radiation exposure in PET/CT. Many
improvements should be pursued when performing PET/CT studies in children to reducerisks, not only from radiation exposure, but also from the need to perform exams sometimes
under general anaesthesia, that should also be reduced. These strategies involve carefulpatient preparation and the use of appropriate immobilization techniques, working with carers/comforters and family to prepare the patient, assuring compliance to recommended
paediatric activities and the use of paediatric-specific CT imaging parameters. (Parisi et al.,2017; Hansen et al., 2022).
(283) Eliminating unnecessary examinations reduces radiation exposure. Each PET/CT
examination should be clinically justified. Referring physicians should order the imaging
study that is standard in clinical practice. To help them, both the American College ofRadiology and SNMMI have been developing a set of evidence-based, expert
recommendations ‘Appropriateness Criteria’ (Jadvar et al., 2017). For specific pathologies,
including in children, evidence-based guidelines can be found in many scientificorganisations, such as the National Comprehensive Cancer Network (NCCN) or theEuropean Society for Medical Oncology (ESMO). SNMMI also collaborated with The Image
Gently Alliance, preparing some booklets dedicated to the referring paediatricians, in whichradiological protection issues related to nuclear medicine procedures are dealt with, and thus
can help these physicians to further justify their referrals (The Image Gently Alliance, 2022).
(284) Following the current guidelines and using paediatric appropriate
radiopharmaceutical administered doses can optimise radiation dose from the PET
component. Increasing imaging times per bed position facilitates further reduction in77

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administered radiopharmaceutical doses, but it cannot be forgotten that this might increase
the need for sedation. Sedation or anaesthesia may be used for infants, young children and its
related complications should be also considered. Newer PET systems with wider axial fieldof view, or equipped with more efficient detector systems, or certain examination protocols,
allow also to reduce the administered activity (Vali, 2021) and so, if available, should be thepreferred ones to perform PET/CT studies in children.
(285) It has been shown that applying the same adult CT protocols in paediatric patients
can lead to a twice increase in organ and effective doses delivered to the youngest children ascompared with an adult (Brenner and Hall, 2007). To keep children specific CT protocols,
one needs to reduce CT imaging parameter dosages by decreasing mAs and reducing kVp.
For children, it is especially important to choose the appropriate scan field of view, use dose
modulation techniques, and avoid, when possible, multiphase imaging.
(286) When more than one PET/CT scanner is available within a department, paediatricpatients should be assigned to the scanner on which clinically acceptable image quality canbe achieved while imparting the lowest radiation dose.

2941

6.6. Breast Feeding

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(287) There are two potential sources of radiation to breast fed infants. First, theradiopharmaceutical itself may be excreted into breast milk and second, the breast-feeding
woman can be a radiation source irrespective of whether the radiopharmaceutical is excreted
into breast milk. For 2-[18F]FDG dose to the breast feeding child appears to be primarily
related to breast activity, which appears to increase with suckling, versus activity secreted
into breast milk (Hicks et al., 2001).
(288) For PET radiopharmaceuticals labelled with the short lived 15O,13N, 11C PET
isotopes there are no recommended restrictions to breast feeding (ICRP, 2015a Table D1).
For 2-[18F]FDG breast feeding cessation recommendations range from: no interruption(ICRP, 2015a Table D1, Leide-Svegborn et al., 2016), one-hour (ARSAC, 2021), and threehours (IAEA, 2018). These recommendations are primarily based on the dose to the baby
from close proximity to the mother during breast feeding. However, when using the ALARA
principle, for 2-[18F]FDG PET studies these ranges should be accommodated by advising thepatient to breastfeed just before PET radiopharmaceutical injection to maximise time between
injection and the next feeding, or to express the milk before and let another person feed thebaby via a bottle. For 124I labelled PET radiopharmaceuticals, the recommendation is to ceasebreast feeding (NRC, 2018). For a more comprehensive discussion on breast feeding
recommendations related to a variety of PET and non-PET radiopharmaceuticals readers arereferred to Annex D1 of Publication 128 (ICRP, 2015a).
(289) There is minimal data to guide recommendations for non 2-[18F]FDG PET
radiopharmaceuticals. For radiopharmaceuticals not listed, one option is to perform photon
counting on specific samples, although the logistics, as well as the subsequent dose
calculations, may be difficult. Consultation with a nuclear medicine physicist and/or otherappropriate specialists is recommended if administration cannot be postponed in such cases
until breast feeding has ceased.

2967

6.7. Fetal dose

2968
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(290) Ionising radiation diagnostic imaging should be avoided in pregnant patients unlessthe medical justification is compelling. If imaging proceeds the study should be optimally78

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protocolled to reduce fetal dose as low as reasonably achievable (Segall et al., 2010;
Boellaard et.al., 2015).
(291) Noting this, diagnostic 18F related PET radiopharmaceuticals do not generally resultin a high fetal dose. Xie et al. (2016) published fetal doses ranging from approximately 1 to
10 mSv post 2-[18F]FDG injection with the stage of gestation being a contributing factor forthe range (i.e. higher doses in early gestation). Table 6.7, adapted from Stabin (2017),
estimates fetal doses for 2-[18F]FDG and Na[18F]F (18F-Sodium Fluoride).
(292) These data demonstrate two points: fetal dose decreases with gestational age and the
maximum estimated fetal dose for a routine 2-[18F]FDG procedure (e.g. nominal dose of 400
MBq 2-[18F]FDG) would be 9.2 mSv in the less than 3 month gestation period reduced to 6.8
mSv at 9 month gestation. Adult activities for Na[18F]F bone scans typically fall between 185
to 370 MBq (Segall et al., 2010) which, based on Table 6.7 will result in lower fetal doses(i.e. 4.1 mSv to 8.1 mSv for the early fetal period).

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*

Table 6.7. 2-[18F]FDG and Na[18F]F fetal dose by stage of pregnancy.*
Early(< 3months) 3 months
6 months
Radiopharmaceutical mGy MBq−1
mGy MBq−1 mGy MBq−1
2-[18F]FDG †2.3×10-2
2.2×10-2
1.7×10-2
18-2-2
Na[ F]F
2.2×10
1.7×10
7.5×10-3†

Adapted from Stabin (2017)
Dose contributions from mother and fetal self-absorption

9 months
mGy MBq−1
1.7×10-2
6.8×10-3

2987

6.8. Carers/Comforters

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2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012

(293) For the performance of a PET/CT study, patients might be accompanied by carers
and comforters, meaning individuals knowingly and willingly incurring an exposure toionising radiation by helping, other than as part of their occupation, in the support andcomfort of individuals undergoing or having undergone medical exposure (Council of The
European Union, 2013). This definition, in terms of a PET/CT, applies to different sorts ofpersons: regarding children, mainly their parents or other family members, as well as tutors
and other caregivers; and for vulnerable adult patients, with autonomy or not, relatives, closefriends, caregivers or simple institutional volunteers may fall into these categories ofindividuals. Also, considering procedures with radiopharmaceuticals, carers and comforters
concern care to patients either in-hospital or at home, following a procedure with ionisingradiation.
(294) In terms of radiological protection and safety, exposure incurred by carers andcomforters is a medical exposure, and dose constraints are applicable and should beestablished by the national regulator (Council of The European Union, 2013; ICRP, 2008b).
Publications 103 and 105 recommend a dose constraint of 5 mSv per occurrence for carers
and comforters (ICRP, 2007b; ICRP, 2008b).
(295) These dose constraints should be defined mainly to establish protection policies forthe carers and comforters (ICRP, 2008b), but the main issue is that, as any other medical
exposure, before it is undertaken, there is a need to evaluate the specific situation and showthat here is a sufficient net benefit in the involvement of the comforter or carer, taking into
account the direct health benefits to a patient, the possible benefits to the carer/comforter andthe detriment that the exposure might cause (Gill, 2000; Council of The European Union,2013).
(296) Not many studies are available to clarify the level of exposure that carers andcomforters are submitted to when accompanying a patient performing a PET study. At the79

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3013
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EANM Congress in 2019, Kalogianni E. et al. presented a work to quantify the radiation
exposure to carers and comforters from adult patients undergoing a 2-[18F]FDG-PET/CT
study. They have evaluated 23 patients [median age 62 (30–93) years] undergoing a 2[18F]FDG-PET/CT scan, randomly selected. The median injected activity was 342 (224–425)
MBq. All patients had equivalent dose rate measurements recorded at 1 m and 10 patients
had additional equivalent dose rate measurements recorded at 0.5 m and 0.1 m from the mid
abdomen. The median cumulative dose received during a median resting period of 51 (43–61) min, measured at 1 m, 0.5 m, and 0.1 m was 20 (12–39) μSv, 76 (34–201) μSv, and 234(167–301) μSv, respectively. The 95th percentile for these measurements were 33 μSv, 152
μSv, and 286 μSv, respectively. These authors concluded that their work confirmed that carerand comforter radiation exposure levels from 2-[18F]FDG-PET/CT examinations practice are
acceptably low (Kalogianni, 2019) and within dose constraints recommended by ICRP
Publications (ICRP, 2007b; ICRP, 2008b).
(297) Although seemingly low the radiation exposure a carer or comforter, whenaccompanying the performance of a PET examination, is subject to radiological protection
principles of justification and optimisation have to be applied. As such, not only a clear net
benefit for both the patient and the accompanying person should be demonstrated, as well as
there should always be a conjoint effort between health professionals, patient, carer andcomforter, to find the best solution and practices. For example, if a child is comfortable whenaccompanied by an older patient such as a grandparent, instead of the younger parent, thisshould be decided.
(298) Finally, nuclear medicine and imaging departments should prepare and provide
carers and comforters with guidance, preferably written and standardised, on how to act andreduce the exposure in the course of their caregiving activities (Council of The European
Union, 2013).

3038

6.9. Research volunteers

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(299) Investigations involving radiation exposure of humans are an important part ofbiomedical research. The World Medical Association (WMA) has developed the Declarationof Helsinki as a statement of ethical principles for medical research involving human subjects(WMA, 2018). Publication 62 has provided a well-designed guidance on radiologicalprotection of patients or healthy volunteers participating in research (ICRP, 1992).
(300) Before the project is started, its aims, outline, methods, justification (benefit vs risk
evaluation) and detailed plans should be evaluated by an independent body, referred to as the'Ethics Committee'. The Ethics Committee should be formally independent of the individual
investigators proposing the project. It is necessary to explain why the investigation is needed,
the benefit that will result if it is successful, the extent to which that benefit is to the volunteer
or to society at large, the type of benefit, e.g. potentially life-saving, reducing disease andsuffering or increasing knowledge that will give rise to other benefits. On the other hand, theinvestigator must present an assessment of the likely harm to the volunteers from theinvestigation, based primarily on the best quantification of doses available, but modified totake account of any particular characteristics of the group of volunteers that might affect therisk resulting from the radiation, e.g. their age, sex, and state of health.
(301) The risks and likely benefits of the proposed research should be explained tovolunteers in advance. Then a free will informed consent should be obtained from volunteers.
Informed consent includes three key components: (1) that human subjects are informed insuch a way that they understand the risks and benefits of participating in radiation research;(2) that the decision to participate in such research is not because of controlling influences;
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DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

and (3) that their consent is voluntary. The subject has the right to accept the risk voluntarily
and has an equal right to refuse to accept. Some demographic groups are considered to bevulnerable populations, who are particularly at risk for coercion or undue influence in a
research setting. These groups include children, wards of the state, prisoners, pregnant
women, persons who are intellectually disabled or otherwise cognitively impaired, andeconomically or educationally disadvantaged persons. Voluntary accepting or refusing
investigations is difficult to carry out on groups such as on children or those who areintellectually ill or defective, as they cannot give free and informed consent. In exceptional
circumstances, such as when proposed investigations are likely to benefit children or persons
with intellectual disabilities and the risks are sufficiently small, those responsible for suchindividuals might be able to agree to their participation. This might also apply for example
when the proposed societal benefit of the investigation is obviously advantageous andsubstantially exceeds the risk.
(302) Pregnant women should not be asked to take part in research projects involving
irradiation of the fetus unless the pregnancy itself is central to the research, and then only ifother techniques involving less risk cannot be used. The proposed benefit of the study should
be clear and substantially exceed the possible detriment. In this case the full and informed
consent of the pregnant patient must be obtained and it would usually be appropriate to seek
the same from the father. In some investigations it would be prudent to consider the
possibility that a woman may be pregnant but not know it. If so, the protocol involved in theinvestigation should recognise this possibility.
(303) If the subject is in a position of obligation towards the investigators, for example as
an employee, a student or even a patient, or can expect some non-health benefit such as
promotion, special privileges or payment, a difficult situation arises. It is particularly
important in such circumstances that consent should not be influenced unduly and should begiven as freely as possible.
(304) The principal investigator (PI) or sponsor involved in human-studies research
involving ionising radiation should have a working knowledge of the basic concepts ofradiation exposure, absorbed dose, and effective dose (E) or should consult with aknowledgeable medical physicist or radiological or radiation therapy professional. Research
including PET, PET/CT or PET/MRI scans is generally within a range of minor to low dosesof radiation (E = 3–50 mSv) (NCRP, 2020). But some studies including repeated PET,PET/CT, or PET/MRI scans can be in the range of low dose (E = 50–100 mSv). Althoughscientists are not certain about the actual cancer risk at these doses, the amount of radiation
involved in this research may slightly increase the risk of getting cancer later in life. Doselimits do not apply to medical research participants, although a dose constraint needs to beconsidered for 'healthy volunteers'. Optimisation requires that the dose should be kept as low
as reasonably achievable. Research and development of new radiopharmaceuticals must be
supplemented by animal experiments to estimated radiation dose to volunteers. Efforts should
be made to avoid research subjects participating in multiple research studies (with monetary
benefit in mind) to avoid excessive radiation exposures.

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7. RADIOLOGICAL PROTECTION FOR THE PUBLIC(305) Key points in this section:• Patients undergoing diagnostic PET radiopharmaceutical studies generally do not posea significant radiation risk to the public.
• Radiological protection measures such as administered activity, distance, time,shielding, facility design, and restricted access need to be considered to protect other
patients, non-radiation workers, and the general public during the PET
radiopharmaceutical uptake period and during PET/CT imaging.

3110

7.1. Background

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(306) Public radiation exposure includes exposed members of the general public, workers
who are not designated as nuclear or radiation workers, and unintentional patient-to-patient
exposure after PET radiopharmaceutical administration. Public radiation exposure excludes
occupational, medical (i.e. to the intended patient), designated caregiver and natural
background exposures. Please see Section 6 regarding radiological protection of breast-fed
infants from women who have had a recent PET study as well as a discussion on PET
procedures during pregnancy.
(307) Public dose limits are based on the sum of internal and external exposures fromsources related to practices that are justified. The recommended annual public dose limits are:effective dose -1 mSv, lens of eye dose - 15 mSv, and skin dose - 50 mSv (ICRP, 2007b).
(308) Apart from the basic radiological protection practices, such as, maintaining distancefrom the patient, reducing the time spent in close contact with the patient, and using
appropriate shielding whenever practicable, the radiation dose reduction to members of the
public is achieved through a reduction in the patient activity which is due to physicalradioactive decay, which is in the range of minutes to a few hours for the most used PET
radiopharmaceuticals, and biological elimination (i.e. by renal excretion for 2-[18F]FDG).
Specific biokinetics for 2-[18F]FDG, the most used PET radiopharmaceutical, are provided in
Publication 128 (ICRP, 2015a).
(309) Taking this into consideration practical ways to reduce external dose rates frompatients injected with 2-[18F]FDG include:• Consultation with the appropriate regulatory jurisdiction on nuclear medicine relative
to PET/CT facility construction and site design guidelines. These guidelines should
include recommendations on how to reduce public and occupational dose via thespecifications of the facility design (e.g. optimal layout for work flows, plumbing,shielding, etc.) (CNSC, 2010; IAEA, 2018) (see Section 3).
• Adequate combinations of distance from, and shielding of, injection/uptake rooms.
• Limit access to the injection/uptake areas to essential staff and patients i.e. no generalpublic access including those accompanying patient (e.g. family, friends, non-healthcare worker caregivers) unless there are compelling circumstances.
• Dedicated 'hot patient' toilets with shielding from public areas (e.g. waiting room,
adjacent offices etc.)• 2-[18F]FDG dosing by weight or body mass index (BMI), adequate hydration andadopting PET/CT technologies and image processing software/hardware which
produce clinically adequate images with lower injected doses, which will result in a

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lower patient dose and a lower external dose from the patient to others, including thegeneral public, after the procedure (Segall et al., 2010; Boellaard et al., 2015).

3147

7.2. General recommendation on radiation dose to the general public

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3166

(310) In general, radiation dose rates are sufficiently low post imaging in 2-[18F]FDG
injected patients that they do not pose a radiation risk to those around them. For example,
Quinn et al. (2012) estimated a patient post injection 18F dose rate constant of 0.092 μSv m2
MBq-1 h-1 which can be scaled for decay and distances beyond a meter in distance. Taking
this dose rate constant into account public dose limits will not be exceeded. No specific post
imaging restrictive advice is recommended regarding taking public transit or close contact
with the general public, children or pregnant women. More specifically, 'holding' the patient
post imaging in a separate waiting area to allow for further dose rate reduction post 2[18F]FDG PET/CT imaging is not necessary and is not recommended.
(311) The general advice is not to bring children, especially young children, and byextension pregnant women, to the imaging centre and for family/caregivers to wait in thewaiting room during patient uptake and imaging (Cronin et al., 1999; Bartlett, 2013).
(312) Use of unconventional or novel PET radiotracers, which may have longer half-lives
and more complex decay schemes, may require additional external dose rate radiation safety
considerations to reduce doses to the public (Williamson and Dauer, 2014). Normally thiswould be accommodated by lower administered activities but still needs to be consideredespecially in basic, applied and clinical research settings. For example, Williamson andDauer (2014) advises that radiation safety instructions are required when patient 124I activities
are above 160 MBq.

3167

7.3. Radiation dose to non-radiation workers

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3187

(313) Given the relatively short half-lives and biological elimination, radiation dose rates
from 2-[18F]FDG injected patients are generally low post uptake period and imaging.
However, it could be appropriate to decide upon dose constraints that non-radiation workers
should not exceed during a year, relating to the annual dose limits. Patients may be returnedto the ward or go on to other diagnostic testing requiring close contact (e.g. ultrasound).
Bartlett (2013) published expected dose rates to other health care workers post 2-[18F]FDG
PET imaging. The highest dose was to intimate patient contact settings such as intensive careunits with the assumption of one-on-one nursing care for 8 hours for a post 2-[18F]FDG
injected patient. Even in this setting the estimated staff dose was only 77 µSv per patient,well below the 1 mSv threshold for non-radiation workers noting that jurisdictions may set
lower dose constraints. If intensive care unit (ICU) staff routinely manage post 2-[18F]FDG
injected patients, a cumulative dose assessment should be performed to reduce dose andimplement procedures (e.g. staff rotation) in line with ALARA.
(314) Griff et al. (2000) and Earl et al. (2018) published radiation doses from 2-[18F]FDG
injected patients to ultrasound sonographers, these are generally not classified as nuclear orradiation workers. Taking into consideration that it would be at least 2 hours post injection
for an 2-[18F]FDG injected patient to receive an ultrasound study, radiation doses tosonographers are low and well below public dose limits. Earl et al. (2018) estimated asonographer dose of 19 µSv for a 30-minute ultrasound scan. In keeping with the ALARA
principle, and when there are otherwise no compelling clinical reasons, it is recommended to83

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schedule ultrasound exams first and PET scans thereafter, if there are sequential PET and
ultrasound exams ordered on the same day, for the same patient.
(315) Cronin et al. (1999) concluded that even for the highest exposure scenario, i.e.
oncology ward nurses caring for patients undergoing 2-[18F]FDG PET scans, it is unlikelythat any nurse would receive more than 24 µSv day-1 and it is unlikely they would receive
this dose every day at work. In the unlikely scenario where nurses worked daily with post 2[18F]FDG injected patients, dose estimates would be helpful to mitigate dose via strategies
such as staff rotation.

3196

7.4. Patient to patient dose

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(316) The layout and shielding between PET radiopharmaceutical injection/uptake rooms
needs to be considered to reduce patient to patient dose as low as reasonably achievable. This
is noting that an unshielded exposure for one hour at one metre from an injected patient
would result in a low dose in the range of 50 to 60 µSv (e.g. 2-[18F]FDG dose of 400 MBq
and a gamma ray effective dose rate 1 m, of 1.398×10−4 mSv h−1 MBq-1) or lower when
taking decay into account (CNSC, 2018) (see Table 3.1).

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8. OPTIMISATION FOR STAFF

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(317) Key points in this section:• Radiation sources in a PET/CT or PET/MR installation include the cyclotron, the PET
radionuclide generators, the radiopharmaceutical, the CT scanner, sealed sources used
for calibration and quality control, patients themselves, and radioactive waste;
producing the possibility of exposure to the nuclear medicine staff due to irradiation,and external and internal contamination.
• The dose to staff in a PET/CT or PET/MR facility can be optimised by applying basic
radiological protection practices, such as, maintaining distance from the radiation
source or patient, performing operations in the shortest possible time, and using
appropriate shielding whenever practicable.
• Dosing schedules for patients which lower administered activity will reduce staff
exposure.
• The optimisation of the working practice and the application of shielding for the vialand syringe are the most important factors in reducing the magnitude of doses to thefingers. Patient preparation and co-operation are important factors in minimising ofcontact time and in increasing the distance between patient and staff member.
• The most important factor that has decreased staff exposure is the use of automatic
dispensing and infusion systems.
• Whole-body monitoring should be carried out based on monthly measurements, and an
Hp(10) measurement from a dosimeter worn on the upper body will also provide anapproximate indication of dose to the eye lens.
• Dose distribution across the hands varies between individuals, depending on techniqueand the use of shields, but the most exposed area of the hand is usually the tip of theindex finger of the non-dominant hand.
• Monitoring extremity doses with ring dosimeters is recommended. It is important tohave an indication of the maximum dose over the two hands, and measurements on
both hands, with trials using finger stall dosimeters, and subsequent application ofcorrection factors are recommended to achieve this.
• An individual monitoring program for internal contamination should be decided basedon risk assessment.

3235

8.1. Sources

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(318) In a PET/CT or PET/MR facility, apart from the patients and members of the public
accompanying the patient, some staff can have a significant radiation exposure. Staff includes
physicians, nuclear medicine technologists/radiographers in nuclear medicine/CT or MR,
technologists in laboratory areas, nurses, chemists, and physicists, engineers, receptionists,
maintenance staff, managers, cleaning staff. The activities performed are varied and include:• Activities related to radiopharmaceutical production, including cyclotron operation andmaintenance, quality control and dispensing.
• Activities in the PET/CT or PET/MR imaging area related to patient, including
radiopharmaceutical preparation and administration to the patient, escorting of the

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patient, positioning of the patient on the scanner bed, patient imaging, and removing
the patient from the bed.

3247
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3258
3259
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(319) Radiation sources in a PET/CT or PET/MR facility can include the cyclotron, thePET radionuclide generators (68Ge/68Ga, 82Sr/82Rb, and 62Zn/62Cu), the radiopharmaceuticalproduced, the CT, the sealed sources used for calibration and quality control, patientsthemselves, and radioactive waste. Because the facility infrastructure, the protocols and thegroups of personnel that carry out different activities can vary widely between facilities, theimpact of radiation sources on the exposure of staff is reviewed in this section according to
the different activities in a PET/CT or PET/MR facility. Annual occupational doses should beconsidered in conjunction with similar activities in a nuclear medicine facility, like gamma
camera, SPECT, and SPECT/CT diagnostic procedures.
(320) The ICRP recommended dose limits are:• Effective dose limit of 20 mSv per year averaged over 5 consecutive years (100 mSv in
5 years) and of 50 mSv in any single year,• an equivalent dose limit to the extremities (hands and feet) or the skin of 500 mSv in ayear. The equivalent dose limits for the skin applies to the average dose over 1 cm2 ofthe most highly irradiated area of the skin,• an equivalent dose limit to the lens of the eye of 20 mSv per year averaged over 5
consecutive years (100 mSv in 5 years) and of 50 mSv in any single year.

3265
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(321) Publication 147 on 'Use of dose quantities in radiological protection' (ICRP, 2021)
presents a proposed change in operational quantities which is expected to be introduced after
the next set of general ICRP recommendations. In this scheme, the personal dose equivalent
Hp(0.07) to the skin will be changed as the operational quantity to the personal absorbed dosein local skin Dp(local skin). This new operational quantity would be expressed in Gy, and nolonger in Sv. This proposed change will help avoid confusion between doses used to control
tissue reactions (in Gy) and whole-body effective doses relating to stochastic effects (inSv). However, in this report Hp(0.07) expressed in Sv is used as the current quantity used inmeasurements and reported in the literature.
(322) Radiation sources produce risks of exposure to nuclear medicine staff due toirradiation and contamination. Personal dose equivalents Hp(0.07) and Hp(10) have beenreported for different scenarios, including point sources, a uniform planar source resembling
a contaminated surface, and several source volumes contained in plastic or glass receptacles(Delacroix et al., 2002; Amato et al., 2018). To evaluate internal contamination, effective
dose coefficients for inhalation and ingestion have been provided by ICRP (ICRP, 2015b,
2016, 2017b, 2019, 2022).

3282

8.1.1. Risk of exposure due to contamination

3283

8.1.1.1. External contamination

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(323) The use of routine hygienic measures such as wearing gloves and protective
clothing, limits skin contamination. Nevertheless, contamination can often not be completely
avoided in the case of accidental spills or cross-contamination. The best way to limit crosscontamination is to frequently measure contamination during and after a manipulation bymeans of contamination monitors, including exit monitoring for staff, which should beavailable in any location where unsealed sources or contaminated components are handled.

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3301
3302
3303
3304
3305
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3308
3309
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DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

Proper detector location should consider any background source that could interfere themeasurement. It is important that contamination monitors are properly calibrated.
(324) Almost half of the incidents reported in nuclear medicine involve contamination(Martin, 2005). In 23 % of the incidents, skin or clothing of a person handling theradiopharmaceutical became contaminated and up to 26 % of the incidents resulted from spillof radioactive material.
(325) Contact exposure due to external skin contamination depends on the activity
distribution. Dose rates produced by a skin contamination due to a 1 kBq 0.05 mL droplet
and a uniform deposit of 1 kBq.cm−2 for positron emission radionuclides are presented inTable 8.1, including their main emissions.
(326) The contributions due to positron radiation and photons to Hp(0.07) and Hp(10) for
distances of 10 cm and 1 m from an infinitely and uniformly contaminated surface arepresented in Table 8.2 for 18F and 68Ga, that have the lowest and highest maximum energy ofthe positrons in table 8.1. Total absorption thicknesses for positrons are included and should
be considered to reduce Hp(0.07). For photons, dose rates at 10 cm and 1 m are similar
because the increased distance is compensated by the increased solid angle. The Hp(0.07)
produced by the positrons is higher for 68Ga than for 18F, showing their higher penetration
power (Delacroix et al., 2002).
Table 8.1. Personal dose equivalent Hp(0.07) values due to contaminations for different
positron emitters (Delacroix et al., 2002).
Radio- Half life Photon Emission
Positron emission
Hp(0.07) (mSv/h)nuclideEnergy Probability Energy Probability Uniform
0.05 ml(keV) (%)
max(%)
depositdroplet2(keV)(1 kBq/cm ) (1 kBq)
11
C
20.4 min 511
200
960
100
1.95
1.12
13
N
9.97 min 511
200
1199
100
1.90
1.2
15
O
2.04 min 511
200
1732
100
2.00
1.4
18
F
1.83 h
511
194
634
97
1.95
0.788
68
Ga
1.13 h
511
178
822
1
1.81
1.25
1077
3
1899
88
Table 8.2. Exposures (mSv h−1) due to an infinite surface uniformly contaminated with 1
MBq cm−2 and total absorption thicknesses for positrons (Delacroix et al., 2002).
18
68
Parameter
Radiation
DistanceFGa−2
Hp(0.07)
Positrons
10 cm
9.6×101.2×10−1−41m
5.3×10
4.5×10−2
Hp(0.07)
Photons
10 cm
6.8×10−3
6.5×10−3−31m
4.3×10
4.1×10−3
Hp(10)
Photons
10 cm
6.4×10−3
6.2×10−3−31m
4.1×10
3.9×10−3
Total absorption Positrons
Glass (mm)0.9
3.9
Plastic (mm)1.77.2(327) The superficial contamination of the skin by a 68Ga droplet will produce a dose rate
60% higher than a 18F droplet, illustrating the contribution of the higher maximum energy ofthe positron. The localised skin dose rate produced by a 18F droplet of 3.7 MBq is 49 mSv
min−1, while a uniform deposit of the same 18F activity in a 5×5 cm2 square will give 4.8 mSv

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3320
3321
3322
3323
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3328
3329
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3333
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3354

min . If a full decontamination is carried out 10 minutes after the incident, the cumulated
Hp(0.07) values would be 471 mSv at the location of the droplet or 47 mSv over the 25 cm2
area, respectively. Due to the short range of the 18F positrons, laboratory gloves can provide ahigh reduction in the dose rate produced by a droplet.
(328) The influence of contamination area, epidermal thickness, and percutaneousabsorption on skin dose rate conversion factors after contamination withradiopharmaceuticals has been reported (Covens et al., 2013). When doses approach therecommended skin dose limit, the influence of the epidermal thickness and the percutaneousabsorption make it necessary to do a proper evaluation of the equivalent skin doses.
(329) During the period 2007–2013, one of the most significant events notified to the
French Nuclear Safety Authority in nuclear medicine, was due to contamination with 18F,
which led to an equivalent dose to the extremities of 320 mSv (Rousse et al., 2014). During a
10 months survey that included 560 inspections, contamination of the skin was detected in 40(7%) cases (thirty-three 99mTc-labelled radiopharmaceuticals, seven 2-[18F]FDG) (Covens etal., 2012). The majority of the contaminations found were highly localised spots on the palmof the hand, rather than uniform deposits. They were mostly located at the tip of the index
finger of the nondominant hand (67% of the cases). Skin doses to nuclear medicine
technologists due to 18F contamination varied from approximately 0.02 to 20 mSv.
Considering the incidence rate and the calculated skin doses, skin contaminations cancontribute substantially to the total extremity dose of nuclear medicine technologists (Covens
et al., 2012). Furthermore, the skin dose limit of 500 mSv y-1 can easily be exceeded as aresult of the poor efficacy of decontamination and the electron dose contribution at shallow
depths (Covens et al., 2013).
(330) If the quantification of the contamination occurs shortly after the event and the firstdecontamination, the retrospective calculation of the initial activity is not required (Covens etal., 2012). In this case the order of magnitude of the cumulated skin dose can be estimated as:

3355

8.1.1.2. Internal contamination

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(332) For workers, the most frequent route of internal intake is inhalation. Intakes byingestion are not usually expected, since eating or drinking in controlled areas in workplaces
is not permitted and inadvertent ingestion is limited by the use of personal protective
equipment. However, when contamination levels in the workplace environment are
significant, ingestion may occur as a result of contamination of the mouth or lips, or transfer
to the mouth from the hands (EC, 2018).
(333) During the maintenance operations on PET cyclotrons there is a possibility ofinternal contamination, due to the inhalation of dust particles produced by interaction of thebeam with internal components of the cyclotron and during the mechanical operations ofrebuilding the ion source, adjusting or replacing the collimators, and cleaning and rebuilding
the 18F target (Terranova et al., 2011).

Hp(0.07) = 3.42 mSv kBq−1 × AD
where AD is the remaining 18F activity spread over 1 cm2 after the first decontamination(kBq) Therefore, the skin dose limit would be exceeded if more than 146 kBq remained on
the skin.
(331) An accidental 18F contamination has been reported in a person during a routine
cyclotron maintenance procedure (Kairemo, et al. 2016). The accident occurred during target
replacement, when liquid 18F was spilled. Quantitative gamma imaging of two separate spots
was performed with a gamma camera, with doses around 1.7 mSv.

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DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE(334) During maintenance operations within the vacuum chamber, care is needed inminimising the possibility of contamination. Residues and powders coming from all thecomponents previously reported could be present, and the possibility of inhalation cannot be
excluded. All maintenance operations should be carried out bearing this in mind; operators
should wear proper protective clothes, gloves, and a face mask. A point that requires attention
is cleaning of the ion source, when this is internal to the cyclotron. The body of the ion
source, typically made of brass, needs to be scrubbed to remove residues. During thesemechanical operations powders are produced, that present a potential hazard from inhalation.
The deposits on the ion source body come from tantalum, the main component of thecathodes, and contain 182Ta, due to the (n, γ) reactions in 181Ta, induced by the secondary
neutrons. The ion source can be disengaged and cleaned in a laboratory area, within a vented
hood (Calandrino et al., 2010; Terranova et al., 2011).
(335) The potential contaminants that could be of concern for operating personnel during
cyclotron maintenance because they might be found in the metallic particulate are(Calandrino, et al. 2010):• High probability of intake: 97Tc, 56Co, 57Co, 58Co, 60Co, 49V, 48V, 52Mn, 55Fe
• Low–medium probability of intake:109Cd, 65Zn, and 22Na
(336) According to the methodology proposed by IAEA (IAEA, 1999), a decision factor(D) is evaluated with the aim to identify those working conditions for which the committed
dose to any operator is <1 mSv y−1:where Ai,j is the cumulative activity (Bq) handled annually by the worker, for the i-th
radionuclide in the j-th operation, e(g)i, inh is the dose coefficient (Sv Bq-1) for inhalation ofradionuclide i, P is the number of operations performed yearly by the worker, N is thenumber of radionuclides managed, and ffs, fhs, and fps are the physical form safety factor,
handling safety factor and the protection safety factor, respectively. Terranova et al. (2011)
found that the decision factor both for the hospital staff, performing simple routine
operational maintenance, and for field engineers of the cyclotron service was <1, meaningthat for their facility an individual monitoring program was not mandated. In order to have afast ‘yes or no’ screening for internal contamination, they conceived a simplified technique ofwhole body counting using a portable NaI(Tl) spectrometer. In a period of 17 months, fiveoperators were checked with a total of 22 acquisitions, and no internal contamination wasobserved.
(337) A programme of internal contamination monitoring was established to monitor therisk for the maintenance staff due to intake of activated elements in a hospital with two
cyclotrons. 30 to 40 interventions were done yearly, including both preventive andemergency interventions, and involving two to four technicians at a time. Every 6 months,
three to four operators were sent to the whole-body counter. Data from 19 individual
measurements showed only one case of internal contamination, due to long-lived
radioisotopes, measuring a total body activity of 286 Bq of 65Zn. In a few cases, a very low
level of contamination was also observed, likely attributable to gaseous 18F inhaled by theoperators involved in the early morning preparation of 2-[18F]FDG (Calandrino, et al. 2010).
(338) In a study investigating the incorporation risk during all stages of the process
through which a typical PET radiopharmaceutical passes from its production to the final
administration, involving 20 workers, 79 whole body measurements were performed
89

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426

(Eschner, et al. 2000). 38 cases were above the detection limit (50 Bq), and estimated yearly
effective doses exceeded 50 µSv in only 10 of 79 cases and they were lower than 1500 µSv;
7 cases were during 124I tracer development, 2 taking care of scanner quality control andcleaning the rooms in the control area, and one was an incident during production syntheses.
Eschner et al. conclude that internal exposure from routine procedures in a PET centre israther low and that the measured whole-body activities, and conservatively estimatedresulting doses, do not warrant the necessity of incorporation monitoring on a regular basis.
(339) Inhalation of airborne activity can produce internal contamination. When it wasmeasured with a gas flow proportional counter, airborne activity did not increase significantly
over background during routine radiosynthesis. However, a significant increase in 15O
concentration was recorded in the scanner room during the [15O]CO administration andpatient acquisition (Calandrino et al., 2010).

3427

8.1.2. Staff irradiation during patient management

3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444

(340) Unshielded sources and patients are the major irradiation sources for staff working
in the PET/CT or PET/MR imaging areas. The dose rate constant for 18F is 0.143 (µSv m2 h−1
MBq−1) (Madsen et al., 2006). Dose rates from patients at various distances and times after 2[18F]FDG administration are given in Table 8.3. Doses rates range from 2.25 µSv h−1MBq−1
at 0.1 m from the patient immediately after administration down to 0.05 µSv h−1 MBq−1 at 1m after the PET imaging.
(341) Dependence of the dose rates at various body positions and at different distancesfrom the patient has been studied (Chiesa et al., 1997; Benatar et al., 2000). Differences inmeasured dose rates at different positions around the patient could be attributed to thedifference in 2-[18F]FDG distribution, but measurement conditions such as patient positioning
and scatter from the bed, floor and ceiling should also be considered. The dose rates
measured at the head are higher than at the feet (Benatar et al., 2000), as the mean percent of
injected activity to the brain is 3.9% at 33 min after 2-[18F]FDG administration (Jones et al.,1982).

3445
3446
3447
3448
3449

*

3450

Table 8.3. Mean dose rates (µSv h−1 MBq-1) at various distances from the patient at different
time points.
Time after
injection (min)0.10 m 0.25 m 0.50 m 1 m
2m
Reference50
0.04
Chiesa et al., 1997§
120
0.31
0.12
0.047
0.017
Cronin et al., 1999¶
After injection
1.28
0.41
0.15
0.06
Benatar et al., 2000†
1
1.58
1.29
0.86
0.33
0.12
1.07
0.74
0.47
0.17
0.05
Demir et al., 2011ǂ
62±8
0.62
0.39
0.25
0.09
0.03
117±11*After injection
2.25
0.33
0.11
0.05
Pant and*After imaging
0.88
0.15
0.05
0.02
Senthamizhchelvan,
2006†
at 0 m.
from the anterior chest.
ǂ
distance to thorax plane.
§from the abdomen.
¶from the mid thorax.
†

8.1.2.1. Whole-body dose

90

3451
3452
3453
3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE(342) The dose received by staff depends on the time spent in close contact with theradioactive sources and the patients and varies among the different facilities. Durations of thevarious steps reported in several studies are given in Table 8.4, and the total time for theoperations is between 6 and 12 min (Guillet et al., 2005, Seierstad et al., 2007).
(343) Depending on the facility design, radiopharmaceuticals can be received in single ormultiple administration packaging. Subsequently, there is a range of tasks that will be
performed. These include: receipt of the containers, measurement of the total activity of thevial, drawing up the activity in a syringe, moving the syringe from the dispensing unit to theadministration room, injection of the radiopharmaceutical dose, attending to the patient
during the bio-distribution period before the scan, escorting the patient to the PET scanningroom, positioning of the patient on the scanner bed, patient imaging, removing the patientfrom the bed, and escorting the patient from the department.
(344) Although procedures vary from site to site, an indication of whole-body doses
received by the staff performing different tasks can be obtained from Table 8.5, whichcollates reports from various publications. Different distributions of dose have been reported
for each phase of the examinations and are summarised in Table 8.6.
Table 8.4. Time (minutes) per different steps during the PET procedure.
Demir et al.,
Guillet et al.,
2010
2005
Radioactivity preparation
1.8
2.1–2.3
Radioactivity administration
0.8
1.8
Escorting the patients to the PET room 1.3
Positioning within the camera
1.6
2.6
Escorting the patient out of the
2.0
department

]

3469
3470
3471

Kumar et al.,
2012
1.0
-

Table 8.5. Hp(10) received by a technologist during different tasks. Values are mean dose
±SD per examination (µSv).
Chiesa et
Guillet et
Demir et al., Al-Aamria,al., 1997
al., 20052010
et al. 2019
Activity (MBq)
500
345
518
298
Receipt of the containers
0.3±0.4
Fractioning/preparation
0.3±0.1
0.1±0.1
1.2±0.6
Placement of activity into a
0.8±0.9
0.3±0.2
injector
Removing the IV line and
1.0±0.01
interacting with patient after thescan
Injection
2.8±1.8
1.1±1.6
0.9±0.6
0.8 ±0.6
WB emission
1.7±1.5
0.7±1.1
Escorting to the scanner
2.3±0.6
1.7±0.1
Positioning within the camera
1.7±1.2
Patient leaving
0.8±0.2
1.5±0.4
1.4±0.7
Total
5.9±1.2
3.2±2.1
7.6±0.7
5.2

]

3472

91

3473

3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

Table 8.6. Percentage contribution of the different tasks to the Hp(10) dose.
Seierstad et al.,2007
Peet et al., 2012
Task
Mean (Median)
Mean
Dispensing
9%
Collecting radionuclide
34 (33)%
Preparation for injection
5 (0)%
Injection of the radionuclide
25 (23)%
32%
Removing the canula
9%
Setting up patient in bed / Scanning
23 (25)%
18%
Removing the patient / Discharging
9 (9)%
14%
the patient
Other handling of the patient / Others
4 (0)%
12%
Escorting to the hot toilet
6%(345) Values reported for whole-body staff doses from PET examinations are presented inTable 8.7. As the administered activity covers a wide range (250 to 500 MBq), thenormalised dose per injected activity to the patient is also provided. The variation of thisnormalised dose (nSv MBq−1) reflects the different procedures and radiological protection
measures followed in each PET facility, providing valuable information on how local practice
can affect the degree of staff exposure. With regard to the whole process (drawing up,
injection and patient management), mean dose per study ranges between 3 and 14 µSv, withnormalised doses from 5 to 39 nSv MBq−1. These wide ranges reflect differences inmethodologies. Note that in some cases, staff can receive relatively high doses in spite of theuse of good shielding (2.5 cm lead shielded holder for transporting a syringe and 5 cm leadpig for dose injecting) and this has been attributed to prolonged periods of time near thepatient (Marti-Climent and Peñuelas, 2002).
(346) Most PET/CT examinations are analysed using the standard uptake value (SUV), asemi-quantitative parameter. Quantitative PET studies generally involve dynamic image dataacquisition and may also require that blood sampling is carried out. McCormik and Miklos(1993) showed that, when conducting quantitative PET studies, doses received by thetechnologists are higher than when conducting qualitative scans (37 and 14 µSv,
respectively), because the technologist stands next to the patient's torso during arterial
sampling for 5 to 10 minutes. The authors report an average dose of 14.2 µSv per patient forthe blood sampling task. Typical administered activities for PET studies were 370 and 3700
MBq for 2-[18F]FDG and 15O-water. The authors also measured an average whole-body doseof 10 µSv while carrying out blood pressure measurement.
(347) The use of radiopharmaceuticals like [18F]-fluorothymidine (FLT) and[18F]fluoromethylcholine (FCH), among others, can require new techniques of imaging, with
the injection inside the PET/CT room and a dynamic acquisition protocol. The impact of theintroduction of these radiopharmaceuticals on whole body doses has been studied, showing a
10% increase in nurses’ doses, due to the longer time they spent near the patient in the
dynamic protocol, and 15–21% increase for technologists, since they come near the patient
immediately after administration (Dalianis et al. 2015).
(348) Different diuretic protocols can be used to lower bladder 2-[18F]FDG activity andpotentially improve image quality by reducing bladder activity artefacts and avoid invasive
bladder catheterisation (Nijjar et al., 2010). However, when urinary catheters are used forassessment of pelvic disease in selected oncology patients, normal saline is used to flush thebladder via a connection in the catheter tubing. Flushing the catheter periodically throughout

92

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539

scanning, to ensure the remaining urine in the bladder is diluted and the bag drained, resulted
in a dose to the technologist of 0.8 µSv per procedure (Roberts et al., 2005).
(349) When 2-[18F]FDG PET/CT is used for radiotherapy planning, positioning of thepatient on the scanner bed should correspond to the position of the patient in the accelerator
bed during the therapy, using the same fixation tools and therefore a strict control, which can
add a considerable dose to the staff. Since the most time-consuming part of the process is theinitial preparation of the patient in the scanner, if this is carried out before the patient receives
the 2-[18F]FDG injection (as "cold preparation session"), it is estimated that the radiation
doses received by radiotherapy radiographers are reduced by approximately three times (14.1
mSv versus 5.1 mSv) (Carson, 2009).
(350) During PET/CT guided biopsy of 68Ga avid lesions using an automated robotic arm,
2 to 3 hours after injection of 111–185 MBq of 68Ga labelled radiotracer (DOTANOC,
PSMA, or chemokine analogue), the mean radiation exposure from the PET tracer to theinterventionist during the molecular biopsy was 1.13 µSv per procedure, with an estimatedannual whole-body dose of 0.57 mSv (Kumar et al., 2020).
(351) Occupational radiation exposure from myocardial perfusion imaging (MPI) with82
Rb PET, that comprises rest and stress scans performed in a single session, has been
evaluated. The generator, placed on a cart next to the scanner, delivers precalibrated doses via
an intravenous line. PET scan starts 60–120 seconds after. Mean Hp(10) dose to all staff
members for combined rest and stress administration and imaging varied from 0.4±0.4 μSv(Tout et al., 2014) to 0.9 μSv (Schleipman et al., 2006). Mean administered activity was 1110
and 1587 MBq for the separate scans, respectively. This higher dose may be attributed to thehigher administered activities and to the procedure, since personnel move behind a mobile
shield in the scanning room during 82Rb infusion and acquisition instead of moving to thecontrol room. The mean Hp(10) for monthly 82Sr/82Rb generator change was 6 μSv and fordaily generator QC was 1.2 μSv. In the event of a medical emergency, the patient may
require extended close contact with the staff after 82Rb infusion. The Hp(10) readings for 7
min PET scans ranged from 2.7 to 59 µSv, depending on the position relative to the patient
and to the unshielded line; a lead shield would reduce the dose. Due to the short half-life,
approximately half of the dose would be received during the first minute of 82Rb infusion(Tout et al., 2014).

3540

8.1.2.2. Hand exposure

3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556

(352) The dose due to positrons is the principal component of skin irradiation, by a factorof 3–100, depending on the conditions. The use of shields for syringes and vials is necessary
to avoid unjustified skin exposures, that may challenge the skin dose limit (Marengo andRubow, 2023). Thus, the dose rate at contact of a 5 ml unshielded syringe body containing
400 MBq of 18F is 20 mSv min−1, and consequently the annual skin dose limit would bereached in 25 minutes (Delacroix et al., 2002; Vanhavere et al., 2012). There is a wide range
in extremity doses reported in the literature (Table 8.8), and there is no consistent pattern as
to whether the dominant or non-dominant hand is more exposed. Leide-Svegborn (2012)
found that the fingers that got the highest doses were the thumb, the long finger or the index
finger of the dominant hand. Conversely, Covens et al. (2007) found that highest skin dose
was often located on the non-dominant hand, since the syringes and needles were often
supported by that hand during several manipulations.
(353) When the study includes multiple dosimeters on each hand, large variations inpersonal dose equivalent Hp(0.07) are observed (Covens et al., 2007, 2010; Carnicer et al.,2011; Sans-Merce et al., 2011; Wrzesień and Napolska, 2015). Extremity dose values fortechnologists working in the same centre have been found to vary by up to a few orders of93

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE
3557

3558

Table 8.7. Whole-body doses Hp(10) received by a technologist.
Dose
InjectedDose-1
activity (MBq) (µSv study )(nSv MBq-1) Comment
14
Qualitative study
37
Quantitative study
500
5.9
12
320
5.5
17
Various tracers
414
13.3
32.1
Various tracers
370
14.3
38.6
Unshielded syringes
10.7
28.9
Shielded syringes
345
3.01
8.1
Semiautomated injector
370
4.1
11
370
3.34
8.76
0.62
1.7
350
8.8
25
No shielded syringe
518
9.3
20
Before shielding
7.6
15
After shielding
250–400
20.1
370
9.5
25.7
Before optimisation
4.8
13.0
After optimisation
308
2.1
6.8
0.6
1.9
4.2–7
17–19
Automatic dispenser
5–6
21–26
Semi-automated dispenser
D, Drawing up; I, Injection; PM, Patient management.

94

Activity
D + I + PM
D + I + PM
D + I + PM
D + I + PM
I + PM
D + I + PM
D + I + PM
I + PM
I + PMI
PM
D + I + PM
D + I + PM
D + I + PM
I + PM
D + I + PM
D + I + PM
I
PM
D + I + PM
D + I + PM

Reference
McCormik and Miklos, 1993
Chiesa et al., 1997
Benatar et al., 2000
Marti-Climent and Peñuelas, 2002
Biran et al., 2004
Guillet et al., 2005
Roberts et al., 2005
Pant and Senthamizhchelvan,
2006
Seierstad et al., 2007
Demir et al., 2010
Covens et al., 2010
Peet el al., 2012
Kumar et al., 2012
Antic el al., 2014

3559

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

Table 8.8. Extremity dose Hp(0.07) normalised to activity received by technologists, all 2-[18F]FDG unless otherwise specified.
Mean (µSv GBq−1)
Left hand
Right hand
86.7*

Maximum(µSv GBq−1)

Location

187
575
185

483*
334*
340
250
2550

407–419*
39.8–41.9*
2.0–27.5*
1200*
930*

594
422

450
340

5329
850
97
324
560
Tip index finger
3000

276
65

4430
4110

The thumb, long or
index finger of thedominant hand

3560
3561

450
1440
*
†

340
2880

1370
7650

Dispensing from:
Multidose vials
Monodose vial
Dispensing
Dispensing
Injection
Scintigraphy
Dispensing
Injection
Before shielding
After shielding

Tip
Tip

Dispensing
Administration
Patient operation
Preparation
Administration

Index finger

Semi-automatic
dispenser
Automatic dispenser

170–680
200

Activity
Injection

Index finger on the Preparation
palm side
Administration

Hand not specified.
Quantitative coronary perfusion PET with 13N-ammonia.

95

Position of the dosimeter

Reference
Marti-Climent andPeñuelas, 2002
Biran et al., 2004
Guillet et al., 2005

Multiple dosimeters on each handIndex and ring finger of each hand

Covens et al., 2007
Tandon et al., 2007

Multiple dosimeters on each hand

Covens et al., 2010

Second finger of each hand

Demir et al., 2010

Fingertips on both hands

Leide-Svegborn,
2012

Right index finger
Right wrist
Base of the middle finger

Kristoffersen et al.,2010†
Kopec et al., 2011

Multiple dosimeters on each hand

Carnicer et al., 2011;
Sans-Merce et al.,2011
Antic et al., 2014

Index finger base of the dominant hand
All fingertips of both hands
Multiple dosimeters on each hand

Wrzesień and
Napolska, 2015
Hudzietzova et al.,
2016

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
3586
3587

magnitude, related to the level of protection used and to different working habits (Antic et al.,2014).
(354) Dose distribution across the hands depends on several factors, as shown in the
ORAMED project (Sans-Merce et al., 2011). The distance between the radioactive source
and the specific part of the hand is an important factor, as dosimeters that are close to thesource are more exposed. Shields are considered a key factor, reducing significantly the
exposure to those parts of the hands covered by the shield. This has also been shown to be thecase in 99mTc manipulation (Whitby and Martin, 2005). The ORAMED multicentre study
showed that, even when performing the same procedure with the same devices, workers
receive doses that vary significantly from one worker to another due to each worker’s
individual habits. The ORAMED study concluded that overall, the most exposed area wasmore likely to be the tip of the index finger of the non-dominant hand, but this will vary withindividual technique.
(355) The results of the ORAMED project, that also included procedures with 99mTc,
showed that the preparation of 18F is the most critical of the studied diagnostic procedures(Vanhavere et al., 2012): the fraction of workers surpassing the annual skin dose limit for theextremities was estimated to be 23% and 40% for 18F administration and preparation,
respectively; while the proportion exceeding 3/10th of the annual limit was estimated to be 66% and 87% for 18F administration and preparation. Other publications have also reported
cases of workers who could exceed the annual skin dose limit (Hudzietzova et al., 2016).
(356) Finger skin doses to the radiochemists during semi-automated synthesis of 68GaDOTA-NOC and to the physician during injecting have been measured. Mean dose to thebase of left (right) ring finger was 3.02 (1.96) mSv during synthesis and 1.26 (1.03) mSv
during injection. Although the mean dose was higher during synthesis than injection, thedifference was not significant. None of the workers used a syringe shield during handlingradioactivity (Dwivedi et al., 2011).

3588

8.1.2.3. Eye lens exposure

3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
3604
3605
3606
3607
3608
3609

(357) Measurements of the equivalent dose to the eye lens have been made in a few
PET/CT facilities (Table 8.9). Hp(3) normalised to total activity handled ranged between 1.1
and 56 µSv GBq−1 depending on the staff group, but those involved in tracer administration
to the patient received the highest doses.
(358) With regard to eye lens exposure in comparison with whole-body exposure, data
show a great variability. While Kubo and Mauricio (2014) found that the eye lens received
doses that were up to 200% higher than the thorax, Kopec et al. (2011) showed that eye lens
and whole-body doses were comparable with Hp(3)/Hp(10) ranging between 0.7 and 1.0,
suggesting that for medical staff Hp(3) could be estimated from measurements of Hp(10).
These results are similar to those in the publication by Kubo and Mauricio (2014), which
reported a ratio of 2.92 and 0.85 for preparation and injection, showing that during
preparation the eye lens is at a shorter distance to the radiation source, while during injection,
the radiopharmaceutical is closer to the thorax, and the measured dose values on the thorax
were larger than those on the eye lens. Furthermore, during fractionating the activity wastransferred from a shielded device to a syringe that was protected with a shield after
measuring the activity. A multicentric study in nuclear medicine, involving diagnostic
procedures mainly performed with 99mTc and 18F, showed Hp(3)/Hp(10) values ranging
between 0.3 and 2.3, with estimated annual doses to the eye lens from 0.6 up to 9.3 mSv.
Therefore, some doses could be close to or even exceed the three-tenths of the eye dose limit(Dabin et al., 2016). The variation in Hp(3)/Hp(10) between publications is related todifferences in procedures and individual habits. Thus, when preparing the syringes, personnel
96

3610
3611
3612
3613

3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
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3626
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3628
3629
3630
3631
3632
3633
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3637
3638

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

use different shielding that could partially cover them, which could cause heterogeneous
exposure and a large variation in Hp(3)/Hp(10) values.
Table 8.9. Eye lens exposure in PET procedures.
Staff
Normalised dose
Mean
Units
Technical
1.2µSv GBq−1(preparation)
Technical
1.1 ; 6.1ǂ(operation)
Injection (nurses)
3.3
Technologist
56µGy GBq−1
Radiographers
Preparation
Injection
Operators
0.02–
mSv week−1
0.27
Preparation
4.3µSv procedure-1
Injection
3.0
Injection
Injection
Dispensing

199*
54*

Hp(3)/Hp(10) Reference
0.9

Kopec et al., 2011

0.7 ; 1.1ǂ
0.9
0.15–1.56
2.92
0.85
0.3–2.3

Leide-Svegborn, 2012
Walsh et al., 2014
Kubo and Mauricio,
2014
Dabin et al., 2016†
Guiu-Souto et al., 20160.56

µSv day−1

Marti-Climent et al.,2018
Wrzesień, 2018a

Maximum.
Nuclear medicine data including PET.
ǂ
Data from two centres.
*†(359) During a [68Ga]Ga-DOTA-TATE procedure, the maximum normalised personal eye
dose equivalent values (Hp(3)/activity) reported for 68Ge/68Ga generator elution, theradionuclide labelling peptide procedure, the dispensing of activity for the patient, and theradiopharmaceutical injection were 80, 72, 274, and 128 µSv GBq−1, respectively (Wrzesień
and Albiniak, 2018). Depending on the work load, annual exposure of the eye lenses toworkers preparing and injecting the radiopharmaceutical may exceed the eye dose limit for
the eye of 20 mSv. In contrast, maximum annual dose (extrapolation of quarterly results) for
nuclear medicine and PET technologists has been estimated at 3.68 mSv for Hp(3), with acorresponding value for Hp(10) of 4.72 mSv (Demeter et al., 2019).
(360) The impact of laboratory protective eyewear (made of about 2 mm polycarbonate)
for the reduction of the eye lens dose while handling different radionuclides has beenmeasuredonphantoms
throughthetransmission
factor18(Hp(3)protected_dosimeter/Hp(3)dosimeter_without_protection). This was 0.99 and 0.65 for F and 68Ga,
respectively. The high transmission factor (lack of effect) for 18F is caused by the facts that 1)
most positrons are already stopped within the syringe and do not have enough energy left toaffect the Hp(3) measurement outside the eyewear, and 2) the eyewear has almost no effect on
the remaining 511 keV photons. In contrast, for 68Ga with its much higher positron energy, alarger fraction of positrons reach the eyewear and are only partially stopped there. Thus, theeye lens dose (per MBq) will be higher for 68Ga than for 18F due to the remaining positrons(Bruchmann et al., 2016).
8.1.3. Staff irradiation during radiopharmaceutical production

97

3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
3653
3654
3655
3656
3657
3658
3659
3660
3661
3662
3663
3664
3665
3666
3667
3668
3669
3670
3671
3672
3673
3674
3675
3676
3677
3678
3679
3680
3681
3682
3683
3684
3685
3686
3687
3688

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE(361) Activities performed by staff during radiopharmaceutical production include
cyclotron operation, the synthesis of the compound, its quality control, and finally its
distribution to a PET/CT or PET/MR facility. In clinical routine, the synthesis is performed
using automatic synthesis modules designed for the different PET radiotracers, placed inshielded hot cells. When the product is distributed to other centres, it is automatically
prepared as single or multiple administration syringes or vials and placed in shieldedcontainers. When the compound is supplied in syringes to the same centre, the process is notalways as automated as when the distribution is carried out in other centres. Before the
distribution, a sample of the radiopharmaceutical should be delivered to the quality control
laboratory for analysis. Quality control may be performed while the tracer is being
distributed. A secure system must be in place to assure that the tracer has passed quality
control tests before injection to the patient.
(362) The cyclotron, whether with self-shielding or placed in a vault, is managed from theoperating console in a room designed to meet local regulatory dose limits. Therefore,
personal exposure during operation of the cyclotron should not be a cause for concern.
Neutron equivalent dose rate measured with a Bonner sphere system in the laboratory next tothe vault of an 18 MeV Cyclotron was 0.26 µSv h−1 (Fernández et al., 2007). However,exposure to radiation must be considered when accessing the different activated parts of thecyclotron. This is done during scheduled preventive maintenance or during unscheduled
maintenance, including repairs. Activation products in the targets and other metallic parts ofthe cyclotron can produce high dose rates. Some activation products can deliver high dose
rates even 24 hours after cyclotron operation.
(363) Dose rates at a distance of 1 m from targets after 18F production can be of several
mSv h−1, decreasing to levels of hundreds of μSv h−1 several hours after production of 18F, so
the standard practice might be to carry out any work on targets on Monday in order to allow areasonable time for decay. For maintenance inside the vacuum chamber of the cyclotron,
targets should be disconnected and removed, to avoid unjustified exposure. After that, in
negative ion cyclotrons, the dose rates in close contact with internal components will belimited to a range of several dozens of μSv h−1, particularly if collimators are made fromgraphite, (Calandrino et al., 2010).
(364) External dose measurements carried out over a period of 3 years showed mean
yearly doses to maintenance staff ranging from 609 ± 860 to 732 ± 973 µSv (Calandrino etal., 2010). In another facility, using a radiation monitoring system, with gamma and neutrons
detectors in a fixed position (cyclotron control room, cyclotron zone corridor andradiopharmaceutical production room), the estimated annual exposures of staff operating thecyclotron were 1.39 ± 0.16 mSv and 2.61 ± 0.14 mSv for photon and neutron radiation,
respectively. In the case of employees in the radiopharmaceuticals’ production zone, theannual exposures measured for gamma and neutron radiation were 0.15 ± 0.03 mSv and 0.11
± 0.01 mSv (Biegała and Jakubowska, 2020). Otherwise, for the personnel of the production
laboratory the largest sources of exposure were the activities with the produced isotope.
(365) In the analysis, by Kumar et al. (2017), of the experience of operation of a medical
cyclotron, the most frequent problems encountered were with the ion source, radiofrequency,
and target foil rupture. These problems were solved during interventions by rebuilding the ion
source, changing the fuse of radiofrequency, and rebuilding the target. When there is the needto remove a target from the target port, this operation should be made quickly, since the target
foils (or windows) are emitting a significant amount of radiation. The target should be
brought in shielded workbench and disassembly of the target body and removal of thefoils/windows should be made carefully and rapidly in order to avoid contamination andradiation exposure. After removal of the target window, the radiation exposure to the working
personnel can be reduced by up to 80%.
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(366) Wrzesień and Albiniak (2016) analysed the hand exposure of workers in a single 218[ F]FDG production centre. Measurements were made for operators of the cyclotron, those
who produce the 2-[18F]FDG, and quality control staff. The highest exposure was in thequality control of the radiopharmaceutical with a maximum dose of 0.35 mSv GBq−1. Those
involved in 2-[18F]FDG production were less exposed: exposure of fingertips during a year
was estimated not to exceed 5% of the annual skin dose limit. The operators of the cyclotron
had the lowest values of Hp(0.07): between 0.3 µSv and 0.12 mSv for one working day. In asimilar study involving two production centres, Wrzesień (2018b) showed that automatic
production of 2-[18F]FDG helped optimise radiological protection of personnel, but aspects ofmanual activities performed as part of quality control of the radiopharmaceutical resulted inincreased hand exposure.
(367) Thyroid and eye exposure were also evaluated. The maximum equivalent dose to theskin at the location of the thyroid gland for staff involved in production procedures, quality
control procedures and cyclotron operation was 116, 83, and 62 µSv d−1, respectively; withan estimated maximum annual thyroid gland exposure lower than 30 mSv (Wrzesień, 2018c).
Mean eye lens exposure (Hp(3)) was 30 µSv d−1, but maximum doses were 89, 236, and 70µSv d−1, for staff performing production procedures, quality control procedures and cyclotron
operation, respectively. On the basis of these figures, the estimated annual eye lens exposureof workers performing quality control procedures could exceed the eye dose limit (20 mSv
year−1) (Wrzesień, 2018a). In contrast, in another centre, the estimated annual eye lens dose
for technologists, involved in PET radiopharmaceutical synthesis, quality assurance, andsyringe preparation, was below 1.2 mSv. Where the maximum technologist eye lens dose
measured was 25 μSv week−1, and 6 measurements were below the detection limit of 15 μSv(Marti-Climent et al., 2018). Differences in eye lens doses could be attributed to theworkload, methodologies and protective devices used in PET facilities performing
radiopharmaceutical production.
(368) Demeter et al. (2019) conducted a study involving technologists, that handled
nuclear medicine and PET radionuclides. Radiopharmacy participants included general duty
production and senior supervising personnel, while cyclotron participants included quality
assurance and production personnel. Maximum annual doses (extrapolation of quarterly
results) for radiopharmacy and cyclotron technicians were 0.44 mSv and 1.48 mSv for Hp(3)and 1.24 and <0.1 mSv for Hp(10).
(369) When 2-[18F]FDG is distributed to a PET/CT facility, exposure due to theradiopharmaceutical preparation ready for distribution can also be taken into account as partof radiopharmaceutical production.
(370) In the case of one centre that started with implementation of a semiautomatic systemfor 2-[18F]FDG distribution, exposure to technologists actually increased. However, this was
predominantly due to the amount of activity distributed (Marti-Climent and Peñuelas, 2002),
and the dose relative to the manipulated activity remained similar for the whole-body (2.5
µSv GBq−1) and decreased for finger exposure (155 µSv GBq−1).

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8.2. Measures to optimise staff radiological protection

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(371) Optimisation of radiological protection for PET and PET/CT of staff, and patients,
involves selection and installation of equipment, design and construction of facilities, choiceof optimal equipment settings, day-to-day methods of operation, quality control programmes,and ensuring that all personnel receive proper initial and career-long training. The radiationdose levels that patients receive also have implications for doses to staff.

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DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE(372) In the same way as for other radiological imaging techniques (ICRP, year1), as newimaging equipment incorporates more options to improve performance, it becomes more
complex and less easily understood, so operators have to be given more extensive training.
Ongoing monitoring, review, and analysis of performance is required that feeds back into theimprovement and development of imaging protocols. Several different aspects relating to
optimisation of protection should be considered. The first is collaboration between the staff
involved in the process, each having key skills that can only contribute to the processeffectively when individuals work together as a core team. The second is appropriate
methodology and technology, with the knowledge and expertise required to use each
effectively. The third relates to organisational processes that ensure required tasks, such as
equipment performance tests, patient dose surveys, and review of protocols are carried out(ICRP, year1). Aspects related to methodology and technology, teamwork, training and skills,
as well as organisation are dealt with in other sections. This section focuses on operational
optimisation measures.
(373) PET procedures are recommended to be performed in dedicated facilities using
appropriate protection tools. Continuing improvements in PET technology is allowing
increased patient throughput. Although this may lead to a corresponding increase in exposureof technologists, improvement in protection methods may allow reductions in exposure.
Rotation of these staff is important to allow for shared higher exposures across the pool oftechnologists, when possible.
(374) The most important factor that has decreased staff exposure is the use of an
automatic dispensing and infusion system, as automation reduces Hp(0.07) up 95% (Covens
et al., 2010). The dose to staff in a PET/CT or PET/MR facility can also be minimised byapplying basic radiological protection practices, such as, maintaining distance from theradiation source or patient, performing operations in the shortest possible time and using
appropriate shielding whenever practicable. Additionally, dosing schedules for patients withlower administered activities will reduce staff exposure.
(375) Greater attention to optimisation should be observed when patients may require
greater staff attention, such as paediatric patients or patients requiring assistance.
(376) Protective measures that should be considered to minimise the dose received by staff
are as follows:(377) General measures:• Operational protocols, including the use of shielding devices, should be evaluatedcarefully. When such protocols are established, they should be practised throughappropriate training programs. It has been noted that - even when performing the sameprocedure with the same device - exposure can vary significantly from one worker toanother due to each worker’s individual habits (Carnicer et al., 2011).
• The application of shielding for the vial and syringe is the single most important factor
in reducing the magnitude of doses to the finger tips (ICRP, 2008a).
• Any tool increasing the distance (e.g. forceps, automatic injector, cradle to sit the PET
syringe injection pig) between the hands/fingers and the source is effective in dose
reduction (Sans-Merce et al., 2011).
• Use of an automatic dispensing and infusion system is desirable, as automation reduces
exposure (Kollaard et al., 2021).

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(378) To prevent the contamination risk:• Use personal protective equipment (PPE), like gloves, lab coat, splash shielding as
appropriate.
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DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE(379) Staff should be instructed and trained to maximise the distance between themselvesand hot patients and to use the protection of shielding:• Practice doing procedures with inactive materials.
• Minimise contact with the patient after radiopharmaceutical injection, reducing timeand increasing distance.

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(380) The wearing of personal protective aprons is not useful due to the high energy of theannihilation radiation as they will only reduce the dose by a few percent (Seierstad et al.,2007; Leide-Svegborn, 2010); however, an apron will be required if protection against CT xrays is needed (e.g. in case of problems with injecting contrast agents during a CT scan).
(381) The ORAMED project, which involved 17 PET/CT facilities and evaluated hand
exposure during both preparation and administration of 18F-radiopharmaceuticals, identified
several good and bad practices (Carnicer et al., 2011): low doses were related to welloptimised procedures or working habits, such as, the use of appropriate shields for syringes
and vials; while high doses were associated with either failure to use suitable means ofradiological protection, usually a shield, or inappropriate use, for example, injecting with ashielded syringe, but placing fingers next to the needle as a guide. Analysis of the factors that
affected the maximum skin dose showed that the most important factor was the shield, bothfor the vial and for the syringe, and that good working habits were more important thanexperience. The importance of an individual technologist's personal habits has been
corroborated by other studies (Covens et al., 2007; Sans-Merce et al., 2011; Hudzietzova etal., 2016).
(382) Active personal dosimeters that can give faster feedback of the radiation field will
always be useful in helping to reduce doses, especially for personnel involved in cyclotron
maintenance or setting up a new radiosynthesis. They have also been used in a clinical setting(Peet et al., 2012).
(383) Another approach to controlling the magnitude of staff exposure in a PET/CT
facility is to rotate the staff members performing particular duties associated with higher doselevels (Antic et al., 2014; Alenezi and Soliman, 2015).

3813

8.2.1. During radiopharmaceutical production

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(384) Preventive maintenance should be scheduled at times when residual activity will beat the lowest point (e.g. last run on Friday - maintenance on next Sunday or Monday). During
cyclotron maintenance, prior to starting on any work, a radiological survey should be carriedout around the cyclotron to assess the level of hazard. If manipulation of the target isrequired, the main hazard is from beta particles due to their high stopping power (shortrange). Therefore, finger contact with activated parts should be avoided, and suitablehandling tools should be used wherever possible (Martin et al., 2018). Staff should wear
gloves and single use filtered masks (class FFP3), to prevent the inhalation of activated dust
particles. Use of an additional active personal dosimeter, with the alarm level set to a defined
integrated dose, can be helpful at least during phases when routines are being established or
modified (Calandrino et al., 2010).
(385) During radiopharmaceutical production:• Use fully automatic synthesis modules to minimise contact with the high activity
managed during the radiopharmaceutical production.

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• Use dedicated hot cells for each radiopharmaceutical to provide flexibility anddecrease the possibility of exposure.
• Minimise the activity handled in each step of the production process (cyclotron
production and radiopharmaceutical synthesis).
• Use the remote control of the hot cells to move loaded vials and syringes.

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(386) Doses received during quality control procedures can be an area of concern.
Attention should be paid to the design of the site for radiopharmaceutical quality control inorder to reduce eye lens dose. In particular, the size and positioning of the shielding used(lead glass) should be adjusted to the height of the quality control personnel (Wrzesień M.,
2018a). Staff members performing quality control can be rotated.

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8.2.2. Use of automatic units

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(387) The introduction of automatic dose dispensing and infusion (D&I) units has brought
about a significant reduction in finger and whole-body doses received by technologists (Table
8.10). However, the percentage dose reduction depends not only on the final doses, but also
on the starting point, which might not be optimised. Therefore, an effect on whole body doses
would not be found if the syringe preparation is done behind a higher lead shielding than thatprovided by the dispensing machine. Technicians may also spend more time per day aroundthe bulk source in the injector. There is also the need to carefully consider the modality ofloading the incoming radiopharmaceutical batch on the injector system, since this procedure
may involve significant exposure (given the high activity of the batch), as well as thepotential risk for incidents.
(388) Application of an automated system has been reported to reduce Hp(10) by up to 50% in terms of the dose during tracer administration, resulting in a dose reduction of 20%
during the entire procedure of injection, and escorting and positioning the patient on thecamera. Extremity doses were reduced by more than 95%, down to a mean level of 10 µSv
per GBq. Additionally, finger doses were more evenly distributed across the hand (Convens
et al., 2010).
Table 8.10. Efficacy of automatic dispensing and infusion (D&I) units in reducing staff
Hp(10) and Hp(0.07).
Hp(10)Dose(µSv GBq-1) reduction
3.6
50%

Hp(0.07)
Dose(µSv GBq-1) reduction
10
95%

ActionD&I

System
A

1.4

2.5*

90%

D&I

B

11

87%

D&I
D&I

B
B

I

B
C

90%
12%
40%

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31%

78%

D

77%

96%

I

A, Posijet (Lemarpax); B, Intego (Medrad); C, KARL100 + Rad-Inject (Tema Sinergie).
*
Wrist dose.

102

Reference
Covens et al.,
2010
Schleipman and
Gerbaudo, 2012
Antic et al., 2014
Sánchez et al.,2015
Alnaaimi et al.,2017
Ferretti et al.,2019

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

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(389) In comparison with a semiautomatic system that prepares the 2-[18F]FDG injections
for manual administration to the patient, an automated infusion device that both prepares anddelivers the 2-[18F]FDG dose reduced fingertip doses by 63% for preparation of the vial and
83% for injection (Sánchez et al., 2015). When a self-dispensing system and an automatic
infuser were used respectively by a technician and a physician, effective dose to the wholebody and equivalent dose to the hands were reduced significantly (Ferretti et al., 2019).

3868

8.2.3. During patient management

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(390) Measures to reduce the staff dose during patient management can be grouped
according to the different steps of the procedure.
(391) General measures:• Patient preparation and co-operation are important factors in minimisation of contact
time and in increasing the distance between patient and staff member. Two measures,
where clinically practical, are to encourage patients to empty their bladder and get on
and off beds independently. The task of going to the toilet prior to the PET scan has
been reported to contribute 0.32 µSv to staff whole body dose per patient, which is 6%of the total dose (Peet et al., 2012).
• Maximise the distance to the patients while escorting them from the injection room tothe bathroom, to the scanner for imaging, as well as escorting the patient to the lobby
after the PET scan.
• Minimise close contact time with the patient.

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(392) Measures during patient preparation prior to injection:• The patient should be advised about the whole PET/CT or PET/MR procedure
beforehand, as this will reduce the time of contact when the patient is a source ofradiation.
• When the patient arrives to the PET facility, the verification process should include
patient identification and exam requested, review with the patient that the preparation
instructions were followed correctly to proceed with PET/CT or PET/MR procedure,
and completion of all forms and questionnaires (such as those for intravenous contrast
and MRI safety questionnaire). A good patient identification is important to reduce thedose by avoiding mistakes in tracer administration, preventing unintended andaccidental radiation exposures (Martin et al., 2019a).
• Enquiries about the patient’s pregnancy, or the possibility of pregnancy, as well as
breast feeding status should be made prior to injection.
• Hospitalised patients, or those who require other forms of special accommodation,
should not be scheduled in the same slots of time, at least try to have them evenly
distributed according to the rotation/distribution of staff, to decrease their exposure.
• Patients should be prepared by placing in advance an intravenous cannula in their veinready for administration of activity, which should be flushed with saline. In this way,
the time for performing an injection can be minimised. This also reduces the possibilityof extravasation.

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(393) Measures during injection:

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• The activity of the radiopharmaceutical administered should be the minimum that iscompatible with the clinical purpose.
• When moving the shielded syringe from the dispensing area to the administration
room, syringe holders and a transport cart should be used.
• Syringes should not be removed from shielding when injecting a radiopharmaceutical
into a patient. Although the injection could be done faster without syringe shielding,the total exposure is less with shielding.
• When injecting the radiopharmaceutical:
o an intravenous line should be used,o caution should be taken to ensure that the PET professional is standing on the side of
the shield when injection and flushing the lines and not on the axis, which will placehim/her in the direct beam from the radiopharmaceutical (Figure 8.1).
• When a cradle is used to hold the PET syringe injection pig on a flat surface, to allow
easier administration of the radiopharmaceutical, the technologists can be further awayfrom the radiation source and reduce exposure of their body and hands.

3920

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Fig. 8.1. During transportation and injection, the technologist does not stand on the axis of the syringe
shield (cylinder) which would place her/him direct in the beam from the aperture. Image: Josep M
Martí-Climent. Spain.

(394) Measures during the uptake phase:• Once the patient has been injected in a shielded resting room or taken to a shielded
resting room, the door (if any) of that uptake room should be closed with a sign on it
indicating that the room is occupied, so that staff could not enter accidently.
• Minimise time spent near the patient after administration.
• Patients should be encouraged to drink water and void the bladder when needed during
the uptake phase, although it is ideal for the patient to remain relaxed and still during
the uptake period and void the bladder on the way to imaging.
• Most PET examinations include the bladder in the scanned area of the patient (forexample, 2-[18F]FDG oncological scans), and since radioactivity accumulates in the
bladder, the patient should void to clear this radioactivity. Approximately 20% of
administered activity is excreted within the first 2 h (Jones et al.,1982; Mejia et al.,
1991; Madsen et al., 2006). This reduction of activity in the patient, used primary to
reduce the patient dose, can be considered as a measure to reduce the dose received by
the staff and also by any person accompanying the patient and by the public after thepatient leaves the PET facility.
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• Hence, in order to minimise staff exposure, the patient should be asked to empty their
bladder before the scan and just before leaving the department.
• In order to guide patients from the uptake rooms to the toilet, include a line on the floor
if the toilet is not immediately adjacent to the room. Staff should not accompany thepatient to the toilet.
• Any un-necessary movement during the uptake phase should be avoided.
• Patients should be viewed remotely via a video monitor in the uptake room and in thescanning room. There should be an audio communication system to allow staff to talkwith patients remotely.
• If a staff member needs to attend the patient, it should be considered that dose rates
measured at the head are significantly higher than at the feet of the patient (Benatar etal., 2000).

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(395) Measures during the imaging phase:• Distance from the patient should be maximised when escorting and positioning thepatient.
• Minimise close contact time with the patient.
• Staff positioning is also another measure to reduce their exposure. Thus, unless thepatient needs special assistance, it has been recommended that, when setting up a scan,
staff should be encouraged to stand in two identified positions: at the end of the bed or
to the side of the gantry (Peet et al., 2012). Another possibility is to allow remoteadjustment of the scanner bed position to be possible from the control room.
• When performing continuous bladder irrigation in evaluating pelvic pathologies(Garcia Vicente et al., 2010), the technologist fills the bladder with physiologicalsaline and then empties the urine back into the bag rinsing the bladder to dilute theurine. To reduce occupational exposure to the technologist performing the technique,apply inverse square law and step back away from the scanning table both during thefilling phase and the emptying phase. In addition, the bag should be shielded.
• When flushing a urinary catheter, placement of shielding around the catheter bag has
been considered to only have a minor effect on total exposure because urinary
catheterisation is only performed sporadically (Roberts et al., 2005).

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(396) Measures after the imaging phase:• When allowing the patient to get out of bed, move the scanner bed from the control
room.
• The patient should be asked to empty their bladder just before leaving the department.

3978

8.2.4. Shielding

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(397) The 0.63 MeV positrons emitted by 18F, which have ranges of 0.9 mm and 1.7 mm
in glass and plastic (Table 8.2), respectively, will be absorbed in the fluid, in the walls of thevial and to a large extent also in a syringe wall. However, the higher energy positrons emitted
by 11C (0.96 MeV), 13N (1.2 MeV), 15O (1.7 MeV), and 68Ga (1.9 MeV) have ranges inplastic of 4–7 millimetres, and to absorb these, PMMA or plastic liners may be incorporated
within vial and syringe shields (ICRP, 2008a). The possibility of producing bremsstrahlung xrays from positron interactions with lead should be considered. When stopping 1 MeV
105

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positrons in lead, 10% of their total energy is converted to bremsstrahlung with a spectral
distribution up to 1 MeV. The amount (but not the max energy) can be reduced by an order ofmagnitude by using PMMA as a first shielding; however, 511 keV photons are the main
source to be shielded from.
(398) In a facility, no syringe shields were used during the handling of 2-[18F]FDG
because the technologists worked faster without syringe shields, and the shield was notconsidered to be very effective for the 0.511 MeV photons, (Seierstad et al., 2007). However,when technologists put into practice important shielding precautions, such as, shielding for asterile syringe and a lead container for the shielded syringe, a significant reduction of themean whole-body dose per study was achieved (9.3 μSv before and 7.6 μSv after shielding
introduction) (Demir et al., 2010). The significant dose reduction due to primary shielding(portable 511 keV-syringe shields of 12.7 mm lead equivalent) and to a secondary shield(trolley-mounted shield of 20 mm of lead) has also been demonstrated by Roberts et al.
(2005). This example shows the importance of using syringe shielding, even if the proceduretakes longer.
(399) Shielding recommendations coming out of the reported studies are:
• For radionuclide manipulation: lead bricks, lead glass, lead transport containers (Anticet al., 2014). For 18F the minimum acceptable thickness of shielding for a syringe is 5
mm of tungsten, and for a vial it is 3 cm of lead (Sans-Merce et al., 2011).
• Containers and 30-cm long forceps; and a 4.5 cm-thick tungsten vial shield and 0.8 cm
of tungsten syringe shield (Antic et al., 2014).

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(400) Examples of good and bad practices during preparation and administration of theradiopharmaceutical using different shielding devices are illustrated in Fig. 8.2: Use of
appropriate shields for syringes and vials (Fig 8.2. a, b, e, and f), inappropriate use of shields
that allow some parts of the hand to directly touch unprotected regions such as the needle andthe bottom of the syringe (Fig. 8.2 c), and no shielding is used for either the syringe or thevial (Fig. 8.2 d, g, and h).

Fig. 8.2. Examples of good administration (a) (b) and preparation (e) (f) practices, and examples forbad administration (c) (d) and preparation (g) (h) practices (Vanhavere et al., 2012). The shielding isused in (a), (b), (c), and (d) with a correct position of the hands, while (c) shows an incorrect positionof the left hand and the right index finger in relation to the shielding, and there is no use of shieldingin (d) (g) and (h).

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8.2.5. Case examples of optimisation

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(401) In the literature there are various reports of dose reduction by means of optimisationof procedures:• Optimisation on the basis of a study of the dose arising from the different phases
within each patient-study resulted in a reduction of the total whole-body dose for all
staff for each patient from 9.5 µSv in the first year of operation to 4.8 µSv in four years(Peet et al., 2012).
• The introduction of an automatic dispensing system and injection and optimisation ofworking practice resulted in dose reduction ranging from 12% in Hp(10) to 96% in
Hp(0.07), as shown in Table 8.10.
• Training specifically for time optimisation has been shown to have an important role.
Antic et al. (2014) showed that training of staff with non-radioactive material
improved efficiency and led to a time reduction of up to 32% during the dispensing
phase, 50% during the injection phase and nearly 40% during the removal of abutterfly needle.

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8.2.6. Summary of measures for optimisation

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(402) Table 8.11 summarises the measures to optimise staff radiological protection in a
PET/CT and PET/MR facility.

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Table 8.11. Practical measures to optimise staff radiological protection in a PET/CT and
PET/MR facility.
General measures
General for irradiation

General forcontamination
Cyclotron maintenanceRadiopharmaceuticalproduction• Operational protocols should be assessed and trained• Shielding for the syringe and vial is the single most important factor in
reducing the magnitude of doses to the finger tips
• Use any tool to increase the distance between the hands/fingers and thesource• Automatic dispensing and infusion systems are desirable• Active personal dosimeters can give faster feedback of the radiation
field, and can assist in lowering doses• Rotate the staff members performing particular duties associated withhigher dose levels• Personal protective aprons are not useful• Use personal protective equipment (PPE), like gloves, lab coat, splash
shielding as appropriate)• Schedule preventive maintenance at times when residual activity will beat the lowest point• Perform a radiological survey around the cyclotron to assess the level ofhazard• Use active personal dosimeter, with alarm level set to a defined
integrated dose
• Wear single use filtered masks to prevent the inhalation of activity• Use fully automatic synthesis modules• Use dedicated hot cells• Minimise the activity handled• Use the remote control of the hot cells to move loaded vials and syringe• Adjust the position of the shield to the height of the quality control
personnel

107General for patientmanagement
Preparation phase

Injection phase

Uptake phase

Imaging phase

After imaging

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE• Promote patient preparation and co-operation to minimise contact timeand in increase the distance• Maximise the distance to the patients• Minimise close contact time with the patient• Patient should be advised about the whole PET/CT or PET/MR
procedure• Verification process should include patient identification, pregnancy
and breast-feeding status, and exam requested, review of whether the
preparation instructions were followed correctly and completion ofquestionnaires, including MRI Safety questionnaire when appropriate• Hospitalised patients, with difficult cooperation, should be scheduled
evenly distributed according to rotation/distribution of staff.
• Instruct the patients to empty their bladder before and after imaging andget on and off beds independently if possible• Prepare the patient by placing an intravenous cannula in their veinready for dose administration• The activity of the radiopharmaceutical administered should be theminimum that is compatible with the clinical purpose• Use syringe holders and a transport cart, when moving the shieldedsyringe from the dispensing area to the administration room
• Syringes should not be removed from shielding when injecting• Use an intravenous line
• The technologist should not stand in the axis of the syringe shield(cylinder) which would place her/him in the direct beam when injection
and flushing the lines• The door of the uptake room should be closed with a sign on it
indicating that the room is occupied• Patients should be viewed remotely via a video monitor• Use audio communication system to talk remotely with patients• Minimise time spent near the patient after administration• Patients should be encouraged to drink water and void the bladderfrequently• Avoid any unnecessary movement during the uptake phase• Distance from the patient should be maximised when escorting andpositioning the patient• If a person is needed to assist the patient, consider the use a lead shield
and that dose rates measured at the head are higher than at the feet ofthe patient• When setting up a scan, unless the patient needs special assistance, staff
should be encouraged to stand at the end of the bed or to the side of thegantry, although it is preferable to move the scanner bed from thecontrol room
• Patients should be viewed remotely via a video monitor• Use audio communication system to talk remotely with patients• When performing continuous bladder irrigation, increase the distance tothe scanning table• When allowing the patient to get out of bed, move the scanner bed fromthe control room
• The patient should be asked to empty their bladder just before leaving
the department

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4042

8.3. Staff dose monitoring

4043

8.3.1. Introductory information

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(403) As described in Section 8.1, staff working in the imaging facilities and theradiopharmaceutical production are exposed to ionising radiation. They can be considered as
occupationally exposed workers, and thus monitoring of the staff is likely to be needed,
depending on the exposure levels. Monitoring can be needed for internal exposures, wholebody exposures and localised extremity exposures.
(404) Individual monitoring is required to verify compliance with dose limits. Extremity,
skin, and lens of the eye monitoring should be undertaken for workers who have a reasonableprobability of receiving per year an equivalent dose higher than 3/10th of one of the yearly
limits (Section 8.1).
(405) For doses above the monitoring level, a monitoring period of one month isrecommended. Shorter monitoring periods can be chosen (weekly monitoring or evenmonitoring per procedure), when setting up new procedures, when optimising working
conditions or when there is a possibility of potentially high exposure.
(406) The dose to the extremities, skin and the lens of the eye need to be monitored insituations where non-homogeneous exposure conditions for which the whole-bodymonitoring does not provide an adequate estimate of these doses.
(407) The skin of the extremities is the limiting organ rather than the extremity itself. An
estimate of the equivalent dose to the skin, Hskin, is normally a conservative estimate of theequivalent dose to the extremities. Therefore, an extremity dosimeter becomes a skindosimeter and shall be designed to measure Hp(0,07) and be placed as close as possible to themost exposed part of the skin surface.

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8.3.2. Routine monitoring of staff

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(408) Whole-body doses of staff should be measured based on continuous whole-bodydose monitoring with doses reported on a monthly basis. This is required not only because
exposures could reach 3/10th of the annual effective dose limit, but because high levels ofradiation exposure could occur during any incidents.
(409) The exposure of the medical staff can be considered homogeneous. This means that
one whole body dosimeter at the height of the chest measuring Hp(10) is sufficient to monitor
the worker. If this Hp(10) value is below the legal limits, it can be assumed that no organ will
be at risk for any stochastic effects.
(410) Radiation doses to the eyes have been found to be similar to whole-body doses,
although some workers - depending on their specific procedures and habits - could exceed thelimit of 20 mSv year−1. A whole-body dosimeter worn on the chest should give a measure ofprobable eye dose levels. If these are high (approaching 6 mSv per year), independentmeasurements of eye doses should confirm the levels of the eye lens doses.
(411) Doses to the extremities and the skin, cannot be estimated from whole-bodymonitoring results, due to the non-homogeneous exposure conditions, so these need to bemonitored. The skin of the extremities is the limiting organ, so an extremity dosimeter
designed to measure Hp(0.07) is required and should ideally be located so that it will measure
the most exposed 1 cm2.

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8.3.3. Dosimeter positioning to monitor the extremity dose

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(412) The extremity dosimeter should be placed as close as possible to the most exposedpart of the skin surface. This is often difficult as the most highly exposed area is not known apriori.
(413) The dosimeter should be oriented towards the radiation source. The dosimeter shallbe worn under protective clothing, especially inside gloves, if such clothing is worn. The
dosimeter could also be worn outside the protective clothing, but under an appropriate
thickness of material that approximates to the type and thickness of the protective clothing.
(414) Depending on the exposure situation, common extremity monitoring positions, suchas the base of the fingers or the wrist, often underestimate the maximum dose. To estimate
the maximum skin dose from a routine dosimeter, a correction factor, for the specific routine
monitoring position, shall be established and employed.
(415) Measurements of hand exposure at multiple locations on each hand have shown
differences between hands of individuals and high dose gradients across the hand (Covens etal., 2007; Carnicer et al., 2011). The magnitude of such dose gradient is determined by theproximity of the fingertip to the unshielded source (Martin et al., 2019b).
(416) Several publications have proposed a multiplicative correction factor to estimate themaximum dose from the reading of a ring dosimeter (Table 8.12). Factors ranging from 2 to9, with the dosimeter positioned on the ring, middle or index fingers, have been proposed.
The most extensive survey in this respect is the ORAMED project, with participation fromPET facilities in six European countries, involving 30 workers in 18F preparation and 30 in
18
F administration. The mean values of the ratios between the maximum dose and the dose at
the base of the index finger and base of the ring finger, for the non-dominant (dominant)hand, were 4 (5) and 6 (5) for preparation and 4 (5) and 6 (5) for administration (Vanhavere
et al., 2012). The study concluded that an appropriate method for routine monitoring of theextremities is to put the dosimeter at the base of the index finger of the non-dominant handwith the sensitive part of the ring dosimeter oriented towards the palm side and to use a
multiplicative factor of 6 to estimate the maximum local skin dose.
(417) The use of wrist dosimeters is discouraged because of significant underestimationand low correlation with the maximum dose (Carnicer et al., 2011; Vanhavere et al., 2012).

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8.3.4. Type of extremity dosimeters

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(418) The dosimeters used for extremity monitoring are generally based on passive
techniques. The dosimeter shall be appropriate for the radiation fields to be monitored, andshall measure the operational quantity Hp(0,07).
(419) Two types of passive dosimeter design are available for fingers: rings, worn at the
thumb, index, middle or ring finger, and finger-stalls, pulled on at either the index, middle orring finger with the detector located at the fingertip. Wrist dosimeters are not recommended.
The technical specifications for extremity dosimetry systems measuring the quantity Hp(0,07)
shall be as defined in IEC 62387 (IEC, 2020) for passive dosimeters.

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8.3.5. Guidance on the use of extremity dosimeters

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(420) In order to provide guidance on the appropriate monitoring for individual staff
members a flowchart is given in Fig. 8.3 relating to requirements based on an initial trial ofwearing a ring dosimeter. Options are given about whether monitoring is necessary based ondose levels recorded.
(421) It is recommended to set up a trial period for a minimum of three months, whereby
the worker is monitored with a ring dosimeter at the base of the index finger. The sensitiveelement should be on the palmer side, so that it will face towards the syringe, vial or other

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source held directly in the hand. If it is clear from the individual practices, which is the most
exposed hand, it is sufficient to monitor only this hand. Otherwise, the trial period should
monitor both hands.

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Table 8.12. Multiplicative correction factor to estimate the maximum dose from the reading of a dosimeter.
Ring position with the TLD placed
towards the palm side
Base of the index finger
Base of the ring finger
Base of the middle finger, right hand

Correction factor
3
6Mean 2.5–3.5
Up to 93
6*Median (mean)
3 (4) Preparation
4 (5) Administration
6

Comment

Recommended for preparation andadministration of 18F and 99mTc

Base of the index finger of the nondominant hand,

1.9–6.3
4.0–7.8
6

Preparation
Administration
Recommendation for PETbase of the index finger*

F and 99mTc
18
F
Recommended for preparation andadministration of 18F and 99mTc
18

Base of the middle finger facing the dorsal side of the handBase of the middle finger

Highest dose location
Tip of the index finger,
dominant hand
Tip of the ring finger of theleft handBase of the index finger

Base of the index finger

112

Fingertips of the nondominant hand

Reference
Morton et al., 2006
Covens et al., 2007
Publication 106(ICRP, 2008a)
Sans Merce et al.,2011

Carnicer et al., 2011
Sans-Merce et al.,2011
Index finger on the palm side Hudzietzova el al.,of the hand
2016
Martin et al., 2018

DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCE

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Fig. 8.3. Flowchart setting out decisions about extremity monitoring options based on a trial periodwith staff wearing ring dosimeters.

(422) If the average monthly dose, without correction factor is less than 1 mSv, regularmonitoring is not necessary.
(423) If the average monthly dose, without correction factor is between 1 and 2 mSv,
routine monthly monitoring can be done by a ring dosimeter that is worn at the base of theindex finger of the more exposed hand. In order to derive the maximum skin dose, amultiplicative factor of 6 is recommended to estimate the maximum local skin dose.
(424) If the average monthly dose, without correction factor is above 2 mSv, the correction
factor can no longer be considered accurate enough, and the real maximum dose across thehand (mostly the finger tip) should be determined. This can be done in a trial period by using
finger stall dosimeters or other methods.
(425) If, as a result of this extra study, the average dose to the most exposed part of thehand is below 12 mSv, the correction factor of 6 can be considered conservative enough, androutine monitoring by a ring dosimeter that is worn at the base of the index finger of the more
exposed hand using this factor of 6 can be done on a routine basis.
(426) If the trial shows that the average dose to the most exposed part of either hand isabove 12 mSv, the correction factor of 6 cannot be considered appropriate. At this point
routine monitoring by a finger stall dosimeter should be done, or an individualised
multiplication factor should be derived from a more extensive monitoring trial comparing thefingertip dose to that at the routine monitoring location of the ring dosimeter, and this applied
for future dose monitoring. If doses to the most exposed parts of both hands are above 12
mSv per month, regular monitoring of both hands is recommended. If a ring dosimeter is113

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used in this way, periodic checks of the fingertip dose should be made to confirm there has
been no change in doses received because of increased workload or change in practices.
(427) If the vial and syringe containing radiopharmaceutical are both shielded effectively
throughout all manipulations, and staff have undergone extensive training in techniques toavoid receiving high doses to the hand, then the ratio between the dose to the fingertip andthat to a ring dosimeter worn at the base of the most exposed finger is likely to be less thansix (Martin, 2016). If this is the case a lower correction factor may be applied to the ring
dosimeter reading, but this must be justified based on evidence from extensive monitoring of
the base and tip of the exposed finger(s) for an extended trial period.

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8.3.6. Skin dose monitoring under contamination

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(428) In cases of skin contamination with radioactive substances, immediate and rapid
decontamination measures are of higher priority than an exact evaluation of skin activity anddose.
(429) Corrections of the measured dose with a dosimeter might need to be made if a
dosimeter is contaminated or in the case of contamination on the protective clothing (ISO,2015):• When contamination is on the skin, there is a proportional relationship (for a given
radionuclide) between instrumentation count rate and skin dose rate for contamination
averaged over a small area (1 cm2 or less). Thus, evaluations where the dose is low canbe done without knowing the individual radionuclide activities, as the uncertainties
will be big anyhow. For higher doses, though, it is important to determine theradionuclide activities so that a more accurate estimation of the skin dose can be made.
• When contamination is on protective clothing (e.g. gloves), it irradiates the skin andcontributes to the skin dose. Its contribution to the skin dose should be quantified,taking into account attenuation through the protective clothing. After quantification, if
its value is higher than the dosimeter reading, it shall be registered as the skin dosevalue obtained for the monitoring period. When the contamination is homogenous
across the protective clothing or located directly at the dosimeter position, thedosimeter reading already takes into account the contribution.
• When an individual dosimeter is contaminated, the dosimeter reading is larger than thetrue dose to the respective individual. If the time the dosimeter has been contaminated,
the activity and position of the contamination is known, this excessive reading of thedosimeter can be determined.

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8.3.7. Internal dose monitoring

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(430) An individual monitoring program for internal contamination should be decided
based on risk assessment. If the decision factor is greater than 1, evaluated according tomethodology proposed by IAEA (IAEA, 1999) and described in Section 8.1.1.2, a techniqueof whole-body counting should be implemented to quantify the internal contamination (inBq). Once the activity (and the timing) is known, an estimate of dose can be obtained withthe help of the OIR data viewer provided by ICRP on the web as supplementary material to
ICRP Publication 151 on 'Occupational Intakes of Radionuclides: Part 5' (ICRP, 2022).

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4205

9. DOSE MANAGEMENT AND QUALITY ASSURANCE PROGRAM

4206(431) Key points in this section:• ICRP recommends an infrastructure exist to ensure appropriate standards ofradiological protection and safety culture for staff, patients and the public.
• The infrastructure should include a legal framework, a regulatory authority, and arobust management system to address radiological protection in PET/CT settings.
• Comprehensive facility or hospital management involvement is key to a successful
PET/CT or PET/MRI radiological protection quality assurance (QA) (aka quality
management) and quality control (QC) program (aka quality management systems).
• A QA program is integrated into the healthcare system that describe what is expectedof the PET/CT or PET/MRI radiological protection program including metrics todemonstrate the goals and objectives of the QA program are being met. Each facility
should have an accident and misadministration review plan.
• Each member of the imaging team has a crucial and defined role.

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(432) Publication 103 entitle 'The 2007 Recommendations of the International
Commission on Radiological Protection' provides general recommendations for radiologicalprotection, for three exposure situations (i.e. planned, emergency and existing) which
includes PET/CT and PET/MRI mainly under the planned situation. The recommendations
start with recommending ‘an infrastructure to ensure that appropriate standards of protection
and safety are maintained’. The infrastructure should include: ‘…a legal framework, aregulatory authority, the operating management of any undertaking involving ionisingradiation (including the design, operation, and decommissioning of equipment andinstallations as well as adventitious enhancement of natural radiation including aviation andspace flight), and the employees at such undertakings.’ (ICRP, 2007b). Regulatory authority
and legal frameworks are paramount for all aspects of radiological protection (ICRP, 2007b).
This same concept is reported in the Safety Guide No. SSG-46 (IAEA, 2018).
(433) The Safety Guide No. SSG-46 asserts that comprehensive facility or hospitalmanagement involvement is key to a successful Quality Assurance and Quality Control
program, to ensure radiological protection and safety related to medical, occupational andpublic exposures (IAEA, 2018). The IAEA has also developed a comprehensive program,Quality Management Audits in Nuclear Medicine (QUANUM) for Nuclear Medicine
Practices, which would be applicable to PET/CT. Publication 103 states that, ‘Verification
procedures should include a review of quality assurance programmes and some form ofinspection’ (ICRP, 2007b).

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9.1.1. Management systems

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(434) The IAEA revised the requirements and guidance in the area of quality assurance forsafety standards on management systems for the safety of facilities and activities involving
the use of ionising radiation (IAEA, 2018).
(435) Publication 75 on 'Radiation dose to patients from radiopharmaceuticals' (ICRP,
1997a) reported: ‘management bodies of the institutions have the responsibility to maintaincontrol and conduct the operation of the radiation exposures’ and that ‘explicit commitment
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of an organisation to safety should be manifested by written policy statements from thehighest level of management, by the establishment of formal management structures for
dealing with radiological protection, by issuing clear operating instructions, and by clear anddemonstrable support for persons with direct responsibility for radiological protection in theworkplace and the environment’.
(436) The function of a management system provides confidence that specified
requirements will be fulfilled (IAEA, 2014b). One of the most important functions of amanagement system in hospital or clinic-based PET/CT or PET/MRI operations isestablishing institutional leadership that supports a 'just culture of quality and safety'.
Management systems have several other responsibilities relating to radiological protection.
(437) Management systems, via organisational leadership, have a responsibility toestablish a radiological protection quality management team that oversees, monitors andanalyses quality indicators. Process improvements are implemented as required, based on thefindings.
(438) Management systems should create policies and procedures that meet regulatory,
accreditation and safety standards. Policies lay out the big picture of what needs to beachieved, whereas goals, objectives and procedures describe how the policies will be
operationalised and monitored to demonstrate congruence with associated policies (IAEA,
2002).
(439) Management systems coordinate and facilitate department quality assessment andimprovement plans. A best practice, quality assurance or quality management program
includes an assessment of policies, protocols, and guidelines to improve radiologicalprotection and safety including dose management and optimisation, performance
improvements on operating equipment, and process improvement and plans for accidents(e.g., spills of unsealed sources) and misadministration of radiopharmaceuticals.
(440) ICRP recommends that management systems be subject to periodic review to guidecontinuous quality improvement, and result in written management requirements. It is bestpractice to include all relevant professional worker’s involvement in developing management
systems and methods to ensure that doses are as low as reasonably achievable (ICRP, 2007b).
(441) Management systems in a PET/CT or PET/MR department should set up asystematic process for analysing and managing reported events, safety incidents andimproving safety as well as part of radiological protection and safety for patients, workers
and the public. Management systems should also establish quality indicators to assess quality
management issues and create an effective action plan to minimise disruption during
implementation of the quality improvement that are found during the assessment phase.
Management system should include review of MRI safety policy, when a change is made to
the safety parameters of the MRI system (ACR, 2020).

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9.1.2. Medical imaging team

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(442) The American College of Radiology and the Association of Physicists in Medicine(ACR-AAPM) Technical Standards, outline the range of personnel who should be included inradiation safety protection i.e.: ‘Radiologist, medical physicist, registered radiologist
assistants, radiologic technologists and all supervising physicians have a responsibility forsafety in the workplace’ (ACR-AAPM, 2018). Please note that the term radiologist also
includes a nuclear medicine physician and the term radiologic technologist includes thenuclear medicine technologist/radiographer as referenced to personnel that should be
included in radiation safety protection. There is a need for the individuals to work together asa team. Each have unique skills and the individuals within the team should have a mutual
respect for the contribution that each makes.
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(443) This same concept holds true when working in a PET/MRI centre, in which, also,
all personnel are responsible for their assigned MRI Safety. Each individual has a
responsibility to work together as a team for the safety of the personnel, patient and public(ACR, 2020).
(444) These personnel contribute to radiation safety, ’by keeping radiation exposure tostaff and to society as a whole 'as low as reasonably achievable' (ALARA) and to ensure thatradiation doses to individual patients are appropriate, taking into account the possible risk
from radiation exposure and the diagnostic image quality necessary to achieve the clinicalobjective’ (ACR-AAPM, 2018).

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9.1.3. Quality assurance and quality control in radiological protection

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(445) Quality assurance (QA) also called 'quality management' or 'quality management
system' can be defined as: all those planned and systematic actions necessary to provide
confidence that a structure, system or component will perform satisfactorily in service.
Quality control (QC) can be defined as: programs and processes related to the QA or quality
management program to verify that structures, systems, and components correspond topredetermined requirements (adapted from IAEA, 2019).
(446) QA/QC programs are driven by senior leadership who are responsible for producing
an overall quality assurance agenda. This agenda includes, continuous quality improvement
goals for the overall health care system, coordination and implementation of improvements
between different departments and services, and analyse relevant data and results to ensure
optimal performance relative to radiological protection. Each member of the imaging teamhas a crucial role in PET/CT QA/QC programs as radiological protection in PET/CT is ashared responsibility of the entire imaging team.
(447) Successful QA/QC programs have assessment activities that determine thequalifications of personal working in the PET/CT department. The QA/QC program will also
include activities that determine the equipment performance as well as processes that
determine the effectiveness of quality control measures. A peer evaluation and technicalreview that assess the clinical images and exam protocols for dose optimisation and quality
will also be incorporated into the program. Each facility QA/AC program should also include
an accident and misadministration review plan (see section 9.2.2).

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9.2. Optimisation of dose to patient

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(448) Planned and systematic actions are needed to provide adequate confidence that allprocesses or services will satisfy given requirements for quality: for example, those specified
in the facilities operational license.
(449) Optimisation of patient radiation dose is one of these planned and systematic actions
to ensure ALARA principles are being followed (IAEA, 2014a). Optimising patient dose isfinding the right balance between administered PET radiopharmaceutical activity and PET
image quality. All member of the imaging team (e.g. Radiologist, Nuclear Medicine
Physician, Physicist, Nuclear Medicine Technologist/Radiographer and Management) canhave valuable input on how to achieve the optimal balance. Recommendations concerning
optimisation of dose to the patient are provided in Section 6.

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9.2.1. Patient dose management

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(450) Optimisation should result in the lowest administered radiopharmaceutical activity
possible while preserving image quality (see Section 6.3).
• It is acknowledged that administered activity and patient throughput are related, but thisshould be monitored keeping ALARA in mind. In the setting of high clinical demandhigher administered activity may prevail to shorten imaging time to allow for higher
patient throughput.
• PET/CT technologies are continually evolving relative to increased detector sensitivity,
hardware and software improvements, and lower dose CT options. Such technologicalimprovements should be exploited to achieve the optimal combined injected PET
radiopharmaceutical and CT patient doses.
• The European Association of Nuclear Medicine (Boellaard et al., 2015) published thefollowing 2-[18F]FDG dosage guidelines (linear-pragmatic approach for adults):(i) For systems that apply a PET bed overlap of ≤30 %, the minimum recommended
administered activity is calculated as follows:
2-[18F]FDG (MBq)=14 (MBq·min·bed−1 kg−1) × patient weight (kg)/ emission
acquisition duration per bed position (min bed−1)(ii)For systems that apply a PET bed overlap of >30 %, the minimum 2-[18F]FDG
administered activity is calculated as follows:
2-[18F]FDG (MBq)=7 (MBq·min·bed−1 kg−1) × patient weight (kg)/ emission
acquisition duration per bed position (min·bed−1)• For systems that allow variable imaging times per bed positions (e.g. reduced time forextremities) the time per bed position for abdomen/thorax should be used in the above
calculations (Boellaard et al., 2015).
• For heavier patients, i.e. > 90 kg, increasing time per bed position is preferred overincreasing injected dose especially for L(Y)SO detector systems (Masuda et al., 2009).
• Lassmann et al. (2014) have summarised European and North American paediatric 2[18F]FDG dosing guidelines.

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9.2.2. Standard operating policy for accidents, radioactive spillage or
misadministration of radiopharmaceuticals

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(451) Medical radiation accidents, spills, and unintended radiopharmaceuticaladministrations may lead to accidental or unintended medical exposure of patients andexposure of staff or the public, and have been reviewed (Marengo et al., 2022). As part of the
Quality Management program, leadership should establish a robust safety system which
includes an accident reporting system to capture near misses, deviations, accidents,
radioactive spillage or contamination incidents and misadministration (e.g., wrong dose,wrong patient, extravasations) of radiopharmaceuticals (Martin et al., 2019a). The safety
program should include policies and procedures to ensure safe practice is being followed
during the clean-up of an unsealed radioactive source spill or any other radioactive accident(e.g. waste accident). It should also include a dosimetric assessment when dealing withmisadministration of radiopharmaceutical. The safety program needs also to include both
regular ongoing training of staff and a continuous quality improvement risk management
strategy related to radiation exposures (public, patient and occupational) from standard
operating policies. Within this risk management strategy leaderships should include
assessment of radiation protection related processes, such as periodic review and updates,
which could be in a form of a review or audit. The IAEA Quality Management Audits inNuclear Medicine (QUANUM) for Nuclear Medicine Practices, would be an example that
could be used in PET/CT (IAEA, 2021b).

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9.3. Optimisation of equipment parameters

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(452) As technologies and protocols evolve dose management strategies should be
reviewed to determine if further dose reductions are possible without adversely impacting on
image quality. Section 6.3 on patient dose optimisation by hardware and software provides
several strategies for optimisation.

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9.3.1. PET subsystem

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(453) New PET/CT technology, as reviewed in Section 2, allow 3D mode acquisition
imaging with higher count statistics. Also, time of flight (TOF) imaging improves signal tonoise ratio, especially for larger patients. All of these factors allow for reduction in thepatient’s dose of the radiopharmaceutical.

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9.3.2. CT subsystem

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(454) CT portion of the PET/CT may specifically be used for attenuation correction andanatomical location resulting in a lower radiation dose and a lower, but acceptable image
quality. Depending on the circumstances it may also be efficient to obtain a standard clinicalquality CT as part of the PET/CT study which may avert duplicate CT studies and be moreconvenient for patients.
(455) Several CT radiation dose quality assurance tools are available (see Section 6.2).
The CT radiation dose can be lowered by adjusting a combination of the following
parameters: lower tube voltage (i.e. kVp), lower tube current (i.e. mAs), automatic tube
current modulation and properly centring the patient, shorter scan length, increase pitch,
collimation, image acquisition, and processing software options such as iterative
reconstruction and thicker slice thickness (ICRP, year2). Hara et al. found that mis centring
the patient by 2.2 cm from the isocentre can increase the CT dose index by an average of
23% (Hara et al., 2013).
(456) Lowering CT dose by adjusting tube current and peak kilovoltage is a good option
noting that this will have to be tailored between different vendor scanners. Hara (2013)
explains, ‘Vendors use different tube current modulation techniques and reconstruction
algorithms to achieve high quality image with lowest dose possible i.e. GE uses noise index
to determine image quality by adjusting the peak kilovoltage and minimum or maximum tube
current’ (Hara et al., 2013; Martin and Sookpeng, 2016). Ensuring the pre-scan image
includes the entire area of interest for the scan will ensure that the ideal tube current module
is used.
(457) A good rule to remember, holding kVp and mAs constant, is that the thinner slices
result in noisier images. While thinner slices may be desirable, in order to maintain constantnoise you will have to increase kVp or mAs or both.
(458) Denoising and Iterative reconstruction techniques can enable CT doses to belowered through the reduction in image noise. The operator will have to actively selectexposure parameters to reduce the doses. In very large practices with multiple PET/CT
system from different vendors, a vendor neutral denoising can be used to reduce the CTradiation dose.
(459) The CTDI dosimetry measurement is based on phantoms of standard size and so thevalue displayed is independent of patient size. As a result, authors have reported that
CTDIvol will underestimate patient dose in small patients and notably paediatric patients.
Optimally CT dose should consider a combination of the patient size and scanner radiation
output. The AAPM Task Force report 204 published, 'conversion factors that were developed
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to be used with CTDIvol, to estimate the dose at the centre of the scanned region' (AAPM,
2011).
(460) The conversion factors give a size specific dose estimate (SSDE), 'which takes into
account the size of the patient, using linear dimensions measured from the patient or patient
image (AAPM, 2011).

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9.4. QA/QC program overview in a PET imaging facility

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(461) A part of the overall QA/QC program aims at ensuring the optimisation of theequipment parameters, in order to systematically guarantee that the performance meets the
specification set by the overall QA/QC for the PET/CT imaging system.
(462) Each member of the imaging team has a specific role and contribution to make to theoverall QA/QC program while noting they work as a team and their individual role will
overlap and rely on other team members. Because of this, it is essential that all members of
the team have a sound understanding of the goal and components of the entire QA/QC
program.
(463) There are many organisations that have published international and national
guidance to assist in establishing a best practice QA/QC program that contributes toradiological protection measures.
(464) The National Electrical Manufacturers Association (NEMA) created a set ofstandards for the performance characterization of PET scanners (see below). Internationalorganisations such as the International Atomic Energy Agency (IAEA) have also issued
publications 'guidelines for the implementation of QA/QC Programmes concerning the
combined medical diagnostic modalities of PET and CT Technologies.' (IAEA, 2009b). For
example, the IAEA (2009b) has published guidelines for routine QC of PET and PET /CT
scanners, including acceptance testing on measuring performance standards against the
manufacturer’s published specifications including best practice for timing and documentation
QA.
(465) AAPM task group 126, ‘has published that the most widely implemented and citedreference for testing PET/CT systems is the NEMA Standards Publication NU 2–Standard
Performance Measurements of Positron Emission Tomography (PET) set forth by the
Medical Imaging and Technology Alliance (MITA) division of NEMA’ (AAPM, 2019b).
The NEMA NU 2 (NEMA, 2018) standard is generally the best performance evaluation of
the PET subsystem because the different manufacturers publish performance specification
based on this standard. NEMA PET procedures require additional testing materials andspecial phantoms to perform the testing.
(466) The International Electrotechnical Commission (IEC) has also produced several
procedure assessments that can be used as best practice which can provide uniform methods
and procedures to measure performance published specifications of PET/CT scanners (IAEA,
2009b).
(467) National and international professional bodies and associations such as the EANM,
the American Association of Physicists in Medicine (AAPM), SNMMI, and the American
College of Radiology (ACR) have developed technical standards, recommendations, andguidance documents (e.g. Sokole, 2010a,b; Hristova, 2017; AAPM, 2019b; ACR-AAPM,
2018) that can simulate procedures that do not require proprietary equipment and software.
These guidance documents, technical standards, and best practice documents can all help toestablish QC tests that can be compared with the manufacturer’s PET/CT publishedspecifications and customise an appropriate QA/QC Programs that provide best practice atyour facility.
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(468) Existing QC technical standards, recommendations and guideline documents fromnational professional bodies are less common for PET /MRI but both the American Collegeof Radiology and Intersocietal Accreditation Commission (IAC) have developed andpublished documents. The AAPM have also provided guidelines for QC Procedures for
associated MRI units that can be used (AAPM, 2010). Recently, the EU-funded HYBRID
project published a survey and an attempt to reach a consensus on the topic of PET/MR QC(Valladares et al., 2019).
(469) National professional bodies such as the AAPM and the ACR have developed
technical standards, recommendations and guideline documents that provide guidelines for
acceptance testing and QC procedures for Computed Tomography scanners (AAPM, 1993;
ACR-AAPM, 2017).

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9.4.1. QC imaging personnel

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(470) Best practice QC program have processes in place that allow tracking of relatively
small changes in the system performance that can contribute to decreased imaging quality
which is illustrated in the results of the Quality Control testing done during the initialacceptance testing, commissioning, daily, weekly, monthly, quarterly or annual testing. These
tests are performed by the Nuclear Medicine Technologist/Radiographer or Medical Physicist
and analysed by the appropriate member of the Imaging team. The Department Medical
Director should be involved with reviewing the results as need be.
(471) The Radiologist or Nuclear Medicine Physician oversees the clinical PET and
PET/CT practice including assessing the diagnostic quality of the acquired images. They play
an important role to ensure and help determine the lowest achievable PET
radiopharmaceutical and CT radiation doses to the patient for specific imaging studies while
preserving overall image quality. They play an indirect role by evaluating the image quality
against the results in the final evaluation of QC tests of instrumentation of both the PET andCT, or PET and MRI and the radionuclide calibrator.
(472) Medical Physicists help to determine the output of radiation dose from the CTcomponent of the PET/CT scanner and adjust imaging parameters of PET and CT (or MRI)
scans to obtain the highest quality image while aiming for the lowest achievable radiationdose to the patient. They also play a vital role in helping optimise imaging protocols for both
PET/CT and PET/MRI. During the commissioning of the PET/CT scanner the physicist helps
to establish CT protocols which can be used for attenuation correction, localisation anddiagnostic purposes.
(473) Nuclear medicine technologists/radiographers customise image acquisition andprocessing software, and operate the PET/CT and PET/MRI scanner, to ensure that the
PET/CT or PET/MRI operate as expected and achieve expected predetermined injectedradiation and CT patient doses. Vendor protocols are customised, based on site specific needs
and factors, to optimise both image quality patient dose.
(474) Boellaard et al. (2015) state ‘PET is a quantitative imaging technique and therefore
requires a common quality control (QC)/quality assurance (QA) procedure to maintain theaccuracy and precision of quantitation. Repeatability and reproducibility are two essential
requirements for any quantitative measurement and/or imaging biomarker’.
(475) The QA/QC program is generally overseen by Medical Physicists who assist in arange of activities including pre-acquisition equipment assessment, acceptance testing,routine QC procedures and trouble-shooting unexpected equipment events. They may also be
involved with tailored software and hardware solutions for research protocols and thisactivity involves assessing such protocols to ensure they meet the ALARA principle. When

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performing QC testing that will be used for radiation therapy treatment planningcollaboration with a radiation therapy physicist is recommended (AAPM, 2019b).

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9.4.2. QC process overview

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(476) PET/CT equipment should undergo manufacturer, operator, and regulator
recommended, and depending on the jurisdiction, required surveys/testing by qualified
individuals at specified periodicities. This survey is to ensure that the equipment isfunctioning properly and producing optimal imaging at the lowest radiation doses possible tothe patient.
(477) There are three components which make up an equipment QC program or quality
management program: acceptance testing, periodic routine testing sometimes called
performance testing, and annual testing. These three QC program components are intended toverify that the specific predetermined criteria are met at installation, the system is optimally
performing properly, and that the images produced are accurate, reproducible and of highquality.

4537

9.5. Components of QC program

4538

9.5.1. QC acceptance testing on equipment

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(478) The first component of a QC program is acceptance testing, which happens
following equipment installation and should be performed on all equipment used in the
PET/CT or PET/MRI department. The acceptance testing of the PET/CT or PET/MRI
scanner and all other equipment needs to be completed prior to clinical imaging.
(479) The ICRP Publication 60 defines an acceptance test as a ‘test carried out at therequest and with the participation of the user or his representative to ascertain bydetermination of proper performance parameters that the instrument meets the specifications
claimed by the vendor’ and recommends that an acceptance test be carried out at the time of
installation and when appropriate after major service (ICRP, 1991).
(480) Acceptance testing establishes baseline performance parameters which can be used
to track changes and trends in future performance (IAEA, 2009b; AAPM, 2019b).
Acceptance testing outcome data also helps in determining optimal operating parameters forclinical procedures.

4552

9.5.2. QC periodic and performance testing on equipment

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(481) The second component of a QC program is routine periodic which generally
includes daily, weekly, monthly testing and the quarterly performance testing to monitor thetechnical performance (follow-up measurements). These tests include assessing for
performance trends to ensure compliance with regulatory agencies and recommending
bodies, as well as to evaluate if the scanner performance has deviated from the initialassessment (AAPM, 2019b).
(482) Unscheduled performance testing should occur prior to recommencing imaging on apatient after PET/CT repairs or part replacement (e.g. a new CT tube) as well as after recalibration or software/hardware upgrades.
(483) Performance testing is part of a QC program that periodically evaluates theperformance of the PET/CT scanner. This testing generally happens after quarterly
preventative maintenance and periodic scheduled calibrations. Generally, it is set up on a122

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timeframe that is established according to manufacturer’s recommendations and according tobest practice recommendations established by professional and national accreditation bodies.
(484) As with all parts of aspects of the QC program annual testing serves an importantcomponent of the overall program, with service engineers ensuring that the system isperforming within the manufacturer published specification during maintenance testing,nuclear medicine technologists/radiographer and medical physicists also perform specificannual QC tests (ACR, 2017). Annual QC testing can detect possible equipment failures
before they create an image quality problem (ACR, 2017). Annual QC testing also illustrates
important information that can contribute to the optimisation of medical dose to the patient
and the ability to continue to find ways to improve image quality with the ALARA principle.
(485) In addition, PET radiopharmaceutical dosing schedules should be periodicallyreviewed to ensure optimisation of the administered activity. Dose delivered for the CT or
related to the CT protocols should be also verified annually.
(486) Annual Testing of the PET, CT or MRI subsystem of the scanner by a medical
physicist trained in each of the specific subsystem is essential to a successful Quality
assurance program.

4581

9.6. QC Testing PET, PET/CT, or PET/MRI

4582

9.6.1. QC Acceptance testing

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(487) Acceptance testing is a legal, regulatory or policy requirement in many countries.
This testing is performed to ensure that PET/CT scanners, including hardware and software,
are installed and set up properly according to manufacturers and industry publishedspecifications. Acceptance testing should always be performed by a qualified andknowledgeable medical physicist with expertise in both PET and CT (Rausch et al., 2014;
ACR-AAPM, 2018).
(488) Acceptance testing guideline has been published by several organisations including
AAPM, EANM and IAEA for PET/CT scanners (Table 9.1). Acceptance tests of the CT partof PET/CT scanner systems have been described in an IAEA document (2009b) (Table 9.2),
and performance evaluation of the CT in reports by AAPM and ACR (ACR, 2017; AAPM,
2019c).
(489) Acceptance testing for a PET/MRI scanner should always be performed by qualified
and knowledgeable medical physicists with expertise in both PET and MRI (AAPM, 2010;
ACR, 2015). Acceptance testing guidelines for MRI have been established by several
organisations including ACR and the AAPM, and establish a baseline performance of theequipment (AAPM, 2010; ACR, 2015). Common QC Acceptance testing on the MRI fromthese organisations include magnetic field homogeneity evaluation, slice-position accuracy,slice-thickness accuracy, RF coil checks, including signal-to-noise ratio and image intensity
uniformity of volume coils, soft-copy monitor QC and MR safety program assessment(Valladares et al., 2019).
Table 9.1. Acceptance and periodical testing for PET.
AAPM
(2019b)Test
Physical inspection
Computer clock synchronization
Daily QC

W
D

123

EANM
(Sokole,2010a,b)
Ac/D
Ac
D

IAEA
(2009b)Ac
Ac
D

ACRAAPM(2018)
D

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Normalization
Q
S
AC/M
Radioactivity concentration calibration
Q
S
M
Q/A
Sensitivity
Ac/A
AC/M
Ac
A
*
Uniformity
A
AC/
Ac/Q
Q/A
Spatial resolution
Ac/A
AC/A
Ac
Q/A
Count rate performanceAC/†A
1. Scatter fraction, count loses and randoms
Ac/AAc
2.Accuracy: Corrections of count losses and randoms Ac/A
Ac
Image quality
Ac
A
Ac/A
Q/A
Energy resolution
AcTime of flight resolution
Ac/D
PET/CT co-registration accuracy/offset calibration
Q
Ac/Q
A
PET/CT scan in clinical modeD
Routine image quality PET/CTQ
D
Image display monitor evaluation
A
Emergency button testing/Safety
AA
Ac, Acceptance; A, Annual; Q, Quarterly; S, Variable, at least six-monthly; W, Weekly, D, Daily.
*
After maintenance/new setups/normalization.
†
After new setups/normalization/recalibration.

Table 9.2. Acceptance and periodical testing for the CT subsystem.
Test
Scattered radiation measurement and shielding verification
CT laser alignment
Table top alignment and positional accuracy and pre-scan view
accuracy
Visual inspection and programme review
Display profile and widthHigh contrast modulationkVp and half-value layer
Radiation dose and image Quality
CT number accuracy
Ac, Acceptance; A, Annual; P, Post Service of related components.

IAEA (2009b)
Ac/A/P
Ac/A/P
Ac/A/P
Ac/A
Ac/A/P
Ac/A/P
Ac/A/P
Ac/A/P
Ac/A/P

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9.6.2. Daily and weekly QC

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(490) The technical parameters of daily and weekly PET and CT QC testing will vary by
manufacturer and should be followed to ensure optimal overall performance and consistency(IAEA, 2014a). These QC tests are usually performed by nuclear medicine
technologists/radiographers at the start of the day and prior to patient imaging, to make surethe scanner is operating correctly. The tolerance is generally set by the manufacturer of thesystem and the outcome of this procedure is generally a visual change or a warning displayedthat lets the nuclear medicine technologist/radiographer know there is a change in detector
uniformity or an electronic error (IAEA, 2009b). These procedures help to ensure that the
PET and CT systems are operating correctly and that the radiation output of the scanner isaccurate (IAEA, 2009b; Boellaard et al., 2015).
(491) When a nuclear medicine technologist/radiographer observes a parameter outside of
the tolerance range or an artefact appears on the PET sinogram it generally means there is aminor drift or a PET detector block defect and there are protocols to help determine theclinical impact of such artefacts (Elhami et al., 2011). The nuclear medicine
technologist/radiographer should repeat the detector normalization test to see if it comes backin tolerance. If the PET/CT does not meet daily QC parameters the appropriate person should
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be called (e.g. medical physicist, equipment vendor etc.,) depending on the malfunction of theequipment or software. Of note major changes or replacement of parts generally require
recalibration of the detector and this should be performed and approved by the e.g. medical
physicist before clinical use (IAEA, 2009b).
(492) The guidelines and frequency of technical parameters, including daily and weekly
MRI subsystem, QC testing have not achieved a consensus between national andinternational bodies but there is agreement that QC testing is beneficial to detect equipment
performance or image quality issues (ACR, 2015; Valladares et al., 2019).

4636

9.6.2.1. Daily QC on PET Subsystem

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(493) The daily PET detector stability test or daily system test is performed to assess thefunction of the detector modules (Elhami et al., 2011; Sokole, 2010b; IAEA, 2014a;
Valladares et al., 2019). Coincidence timing resolution is also recommended daily on Timeof-Flight PET scanners to ensure constancy of the timing resolution (IAEA, 2014a). SomePET systems can perform these tests/measurements automatically over night.

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9.6.2.2. Daily QC on CT Subsystem

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(494) Daily quality control procedures include a system CT warm up procedure which
warms the x-ray tube and should be performed any time the system sits idle for a certain timeframe or when the CT tube temperature falls below an established temperature set by thevendor (IAEA, 2009b; IAEA, 2014a). Another daily CT system procedure verifies that thestructures, systems and components are meeting corresponding predetermined requirements
sometimes called an air calibration procedure. The final step in the daily QC on the CT
system is to use a water filled phantom to check the CT parameters of contrast scale, noise,
uniformity, linearity, high contrast spatial image resolution and low contrast detectability test
(IAEA, 2014a).

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9.6.2.3. Daily QC on MRI sub-component of PET/MRI

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(495) The European commission HYBRID project summarised relevant guidelines andrecommendations for PET/MRI system QC testing. (Valladares et al., 2019). In general MRI
QC should not be overdone. Centre frequency tuning, gain adjustment and shimming are
intrinsically performed on a per patient basis. If no vendor specifications are provided theimage quality test should be performed according to the AAPM or ACR guidelines (AAPM,
2010; ACR, 2015).

4659

9.6.3. Periodic QC

4660

9.6.3.1. QC testing PET subsystem

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(496) More detailed maintenance and PET/CT scanner testing are done usually quarterly,
semi-annually or annually (Table 9.1). Most of the procedures should be performed using ateam approach with both the nuclear medicine technologist/radiographer and the medical
physicist participating in the procedure (IAEA, 2009b). For example, one such quarterly
PET/CT QC test is the normalization scan on the PET subsystem which provides corrections
required to obtain uniform coincidence sensitivity within a single imaging plane (Keim,
2014). According to IAEA, the PET normalization test is critical as, incorrect normalization
data will compromise the image quality (IAEA, 2009b). Some recent PET systems, however,will check the normalization on a daily basis, based on an automatic overnight scan.
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Following manufacturer’s guidelines on this procedure is essential to ensuring image quality.
A good practice is to perform a back-up of the previous calibration file in case there is aproblem with the normalization or if the radioactivity concentration calibration study isoutside of the tolerance parameters that have been established during the acceptance testing.
Manufacturers use different terms to define dose calibrator QC procedures including: wellcounter calibration, radioactivity calibration factors and SUV calibration (IAEA, 2009b).
(497) Hristova describes that 'Implementation of rigorous QC procedures ensures thatbasic data affecting SUVs are verified prior to readouts. In the absence of QC, readouts could
be merely a reflection of technical factors, and conclusions about the validity of PET as an
imaging biomarker may be inappropriate' (Hristova et al., 2017). The efficiency data is usedin calculation of radioactivity concentration and presented as the Standard Uptake Values(SUV) or units of activity per cm3 of decay corrected activity. These Quality Control
procedures should be performed quarterly or whenever the PET part of the system has amalfunction or a part replaced or serviced.
(498) The comprehensive performance testing should include annual QC activities that
determine whether predetermined requirements are being met (IAEA, 2018). The medical
physicist can add the annual evaluation to one of the quarterly PET subsystem QC
performance evaluations. Accurate co-registration of the PET system and the CT system,
which is essential to ensure that proper attenuation correction occurs, should also be
performed at acceptance testing, quarterly as well as annually. AAPM, EANM, IAEA, and
ACR-AAPM all provide international protocols for recommendation for testing of PET
system and their frequency (IAEA, 2009b; Sokole, 2010b; ACR-AAPM, 2018; AAPM,
2019b).

4693

9.6.3.2. QC testing CT subsystem

4694
4695
4696
4697
4698
4699
4700
4701

(499) Annual Testing on the CT subsystem of the scanner by the medical physicist is an
essential component of a successful Quality assurance program. Laser positioning QC is
especially important if PET/CT images are exported and used for RT planning. The annual
CT review should also include a review of the clinical protocols to ensure optimisation of the
CT component in relation to the required level of image quality. QC annual tests of the CTpart of PET/CT scanner systems (Table 9.2) have been described in an IAEA document(2009b). Detailed QC evaluation of the CT systems can also be found in reports of AAPM
and ACR (ACR, 2017; AAPM, 2019c;).

4702

9.6.3.3. QC testing MRI subsystem

4703
4704
4705
4706
4707
4708
4709
4710
4711
4712
4713
4714
4715

(500) In order to discover possible failures, a more frequent testing scheme was suggestedby the HYBRID consortium increasing the image quality test frequency to at least quarterly
to check for minimum acceptable MRI image quality. Due to the large discrepancy between
recommendations, HYBRID suggested a monthly check of the most used coils and whenevera coil is replaced for easy implementation (Valladeres et al., 2019).
(501) In general, no significant interference between MRI and PET subsystems has been
observed (Delso et al., 2011). Simultaneously testing of the PET and MRI subsystems istherefore not likely to be necessary. However, registration of MRI and PET isocentre shouldbe tested to ensure proper image alignment. The PET and MRI alignment should be checkedand calibrated after mechanical changes or repairs and after major software update revisions.
(502) In addition to the HYBRID recommendations, specific site quality assurance andtesting can be necessary. The QC program and frequency should be tailored to the specificneed of the MRI application and use.

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4722
4723

(503) ACR recommends testing the image quality once a year (ACR, 2015). Annual
testing of the MRI subsystem includes: setup and table position accuracy, centre frequency,transmitter gain or attenuation, geometric accuracy measurements, high-contrast spatial
resolution, low contrast detectability, artefact evaluation, visual checklist, magnetic field
homogeneity, slice-position accuracy, slice-thickness accuracy, radiofrequency coil checks,
soft -copy quality control and MR safety program assessment. The medical physicist annual
review of the MRI QC program should also include a review of the sites’ safety guidelines,
practices and policies (ACR, 2015).

4724

9.7. QC testing radionuclide calibrator

4725
4726
4727
4728
4729
4730
4731
4732
4733
4734
4735

(504) Radionuclide calibrators or activity meters are used to assay the radioactive material
to ensure the patient receives the appropriately prescribed activity. Both AAPM and EANM
provide international protocols for recommendation for acceptance and testing ofradionuclide calibrators and their frequency (Sokole, 2010a,b; AAPM, 2012) (Table 9.3).
(505) Harmonised clock accuracy is important between the activity meter, injection timeand imaging times. Accuracy between these functions should be within one-minute to ensure
quantitative imaging accuracy (IAEA, 2009b; AAPM, 2019b). If multiple activity meters arebeing used, they should be cross calibrated to within an acceptable degree of variance (Chuand Simon, 1996).

4736

Table 9.3. Recommended testing for radionuclide calibrators.
Test
AcceptancePhysical inspection
E
A
System electronic
A
Clock
E
A
High voltage
E
A
Zero adjustment
E
A
BackgroundE
A
Check source
A
Constancy
Accuracy
E
A
Stability/ Precision/Reproducibility
EA
Linearity
E
A
GeometryE
Calibration for different containersEand volumes
Supplier equivalence
A

Daily
E
A
A
E
A
E
A
E
A
E
A
A
E

A, AAPM (AAPM, 2012); E, EANM (Sokole, 2010a,b).

Annually

E
E
E

A
A
A
A
A
A
A
A
A
A

A

4737

9.8. QC radiation monitoring instruments and other equipment

4738
4739
4740
4741
4742
4743

(506) Daily radionuclide QC involves different tests (AAPM, 2012; Sokole et al. 2021b).
The acceptable level of the accuracy test is within 5% of the expected value (Chu and Simon,
1996). Constancy, background and voltage testing are also done daily. Annual radionuclide
QC includes most of the acceptance tests.
(507) Radiation monitoring instruments: exposure meter, contamination monitor,
personnel electronic dosimeters or area monitors need routine QC tests performed. QC
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4745
4746
4747
4748
4749
4750
4751
4752

procedure should be performed before each day of use including physical inspection of
detector, measuring unit and cables, battery voltage check and background count. Annual QC
testing includes: sensitivity to test constancy using a long half-life radioactive source,
accuracy, precision and linearity of response are also recommended annually by a qualified
party (e.g. medical physicist) or according to compliance with national guidelines (Sokole etal., 2010b). In some countries radiation monitoring instruments have to additionally becertified on a periodic basis by an External Body, recognised by the Regulatory body.
(508) Additionally, annual QC testing on the scale that a patient is weighed on should bechecked and calibrated if outside of tolerance levels.

4753

9.9. Summary overall QC program

4754
4755
4756
4757
4758

(509) The acceptance and annual report are essential for a best practice in Quality
Assurance and Quality Control programs and should also be kept and available for regulatory
inspections, accreditation reviews and management meeting review. Written reports withfinding from the performance evaluation and the corrective action implemented from theservice engineer should all be kept and available to any member of the Imaging team.

4759

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4760

10. EDUCATION AND TRAINING IN RADIOLOGICAL PROTECTION

4761

4770
4771
4772

(510) Key points in this section:• A health professional that performs PET/CT or PET/MRI procedures must be proficientin radiological protection and safety, not only due to legal requirements, but to guarantee
safety for patients, workers, and public in general.
• This proficiency is obtained through formal education at undergraduate and postgraduate levels, practical training and continuous professional development.
• Many International stakeholders, such as the IAEA, WHO, ICRP, EC, EUTERPFoundation and HERCA have extensively detailed the responsibilities and needs foreducation and training in Radiological Protection, for all groups of health professionals.
• It is important to use existing tools to further develop and adapt a local framework for theeducational programs, that would ensure radiological protection and safety in a PET/CT
or PET/MRI facility.

4773

10.1. Foreword

4774
4775
4776
4777
4778
4779
4780
4781
4782

(511) Although many stakeholders have for many years been developing and publishingdocuments that provide an educational framework for radiological protection, including
specificities for the practice of PET/CT, practices and education across the world differ
widely, and have many weaknesses. This was also acknowledged recently by a consensus
document issued by representatives of European professional societies (Rainford et al., 2022).
(512) Therefore, taking into consideration the observed differences, a need to construct a
standardised framework has led to the revision of current training plans (formal and informal,
as well as continuing education), and these may be implemented in those countries that need
them.

4783

10.2. International stakeholders’ recommendations

4784
4785
4786
4787
4788
4789
4790
4791
4792
4793
4794
4795
4796
4797
4798
4799
4800

(513) The introduction and use of hybrid imaging, such as PET/CT or PET/MRI, linked
with increasing clinical applications of these diagnostic methods, arose challenges early on
for the professionals’ core education and training. Focus on how to implement training foreach of these modalities and their fusion in the same procedures, both formally (i.e. withincurrent educational systems) and informally, became agenda items for discussion among
nuclear medicine physicians, radiologists, nuclear medicine technologists/radiographers andmedical physicists, either locally or in respective professional and scientific organisations.
(514) Traditionally, nuclear medicine technologists educational training programs did notinclude CT or MRI in their curricula. Regarding nuclear medicine physicians, their contact
with these imaging modalities was mainly concerning indications and their role into
diagnostic decisions flowcharts, and not the procedures in depth. This new technology thenposed some equipment operational challenges and potential greater risk to the patientradiation dose, due to the less preparation of these professionals regarding the CT image
acquisition protocol.
(515) There are distinct aspects of exposure that need to be included in radiologicalprotection and safety educational programs and ongoing training for professionals practisingin a PET/CT facility. First, the education and ongoing training on how to deliver medical

4762
4763
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4766
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4768
4769

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4801
4802
4803
4804
4805
4806
4807
4808
4809
4810
4811
4812
4813
4814
4815
4816
4817
4818
4819
4820
4821
4822
4823
4824
4825
4826
4827
4828
4829
4830
4831
4832
4833
4834
4835
4836
4837
4838
4839
4840
4841
4842
4843
4844
4845
4846

exposure to the patient with special focus on dose optimisation and implementation of the
ALARA principle. Related to this, educational programs have to include the concept andproper use of Diagnostic Reference Levels (ICRP, 2017a). Second, education and ongoingtraining on how to reduce the occupational exposure to the staff performing the procedureand strategies to be considered which ensure that the occupational exposure will be as low as
possible. Finally, educational and ongoing educational training to understand public
exposure, for example that related to members of the public in waiting rooms, who may
receive radiation from patients that have already been injected with a radiopharmaceutical(IAEA, 2018).
(516) Each member of the imaging team plays a crucial role in radiological protection,
andradiation safety in PET/CT or PET/MRI. Initial qualification and initial educational
training help ensure a baseline understanding of how to deliver safe and appropriate use of
the medical exposure. Continuous professional development (CPD), education and training
will help to ensure that the imaging team is knowledgeable on how to appropriately optimise
the dose to the ALARA principles, and continuously improve it as well as understanding
MRI safety. As health care professionals, each and every member of the team has different
roles to play in each of these areas of radiological protection and safety.
(517) In 2012, a technical meeting was organised by the IAEA to understand 'the current
status and trends of hybrid imaging using nuclear techniques, hybrid imaging role in clinicalpractice and associated educational needs and challenges' (Kashyap, 2013). Educational
training and requirements for the use of this technology was of key concern for all
stakeholders. It became apparent that education and practice needs differed depending on
what part of the world you were working in.
(518) At this technical meeting, a Strengths; Weaknesses; Opportunities; Threats (SWOT)
analysis was performed for PET/CT, as well as data collected concerning hybrid equipment
availability in regions throughout the world, practices of nuclear medicine and radiology
professional groups and educational training available for both Nuclear Medicine and CT
practitioners. It was concluded that practice and education was very different all over theworld and that there was a need to draw a more standardised approach, appropriate to formal
and on-the-job training, to meet the technological advances in a timely manner, in order toallow for growth in knowledge and clinical benefit for patients. This Technical Meeting, interms of education and training needs, focused more in the clinical curricula for future
medical specialists dedicated to hybrid diagnostic procedures, but also approachedRadiological Protection and Safety topics, as, for instance, reinforcing the need for training
the process of justification of requests for diagnostic procedures with radiation exposure.
(519) Stakeholders and professional organisations are continuously trying to determine
how to best meet the educational demands for medical users of radiation in a timely manner.
At another meeting, hosted both by IAEA and WHO, and held around the same time as theabove-mentioned Technical Meeting, a document was produced, called 'The Bonn Call for
Action', which highlighted 10 actions that would strengthen Radiological Protection forpatients and health care workers. Action Four, called 'the strengthening of radiologicalprotection education and training of health Professionals', states this response will happen by
integrating 'radiological protection into the curricula of medical schools, ensuring theestablishment of core competency in these areas' as well as paying 'particular attention to thetraining of health professionals in situations of implementing new technology' (IAEA and
WHO, 2012).

4847

10.2.1. Recommendations for educational and training from ICRP

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4848
4849
4850
4851
4852
4853
4854
4855
4856
4857
4858
4859
4860
4861
4862
4863
4864
4865
4866
4867
4868
4869
4870
4871
4872
4873
4874
4875
4876
4877
4878
4879
4880

(520) Publications 103 ('The 2007 Recommendations of the International Commission on
Radiological Protection '), 105 ('Radiation Protection in Medicine'), and 113 (' Education andtraining in radiological protection for diagnostic and interventional procedures.') set out theframework for Radiological Protection, providing needs in terms of categorical educational
training to support radiological protection, respectively. Hence, in all these documents it ispossible to identify educational and training issues relevant for PET/CT and PET/MRI.
(521) Publication 113 provides the relevant components and specific details of education,
training and continuous professional development that are essential for all health care
professionals that have a direct role with medical exposure including the specificities for
PET/CT (ICRP, 2009). Education should start at the entry of the professional’s career
through formal education and continue throughout the professional’s entire career in the formof CPD.
(522) Publication 113 states that the specific training related to radiological protection
should be included whenever new equipment or techniques are introduced in the professional
facility (ICRP, 2009). This training and education contribute to the establishment of corecompetency in radiological protection. This specific training also helps the imaging teamestablish safe practices that will contribute to ALARA principle during the medical exposure
to the patient, occupational exposure to the staff and public exposure.
(523) Formal education on radiological protection should be an established part of thecurricula for physicians, nuclear medicine technologists, radiographers and medical
physicists. Regarding physicians, although with different levels of complexity, this educationand training in radiological protection should be applied not only to nuclear medicine
specialists and radiologists, but also to physicians referring patients for nuclear medicine andradiological procedures.
(524) Training and education on radiological protection for all staff should be a standardof practice during new staff orientation and induction procedures and as part of the overall
education that staff receives as employees during their employment. This training should be apart of an ongoing yearly CPD to assess a competency. Because of the highly sophisticatedhybrid equipment that PET/CT or PET/MRI staff are using every day and the evolving role oftechnologies, CPD on new clinical indications, new PET/CT or PET/MRI technology and thedevelopment of new radiopharmaceutical is a common day practice for the nuclear medicine
physician, nuclear medicine technologist/radiographer and medical physicist, andindispensable for them to stay abreast on developing technology.

4881
4882

10.2.2. Recommendations for education and training from other internationalorganisations

4883
4884
4885
4886
4887
4888
4889
4890
4891
4892
4893
4894
4895

(525) In 2014, the Directorate-General for Energy from the European Commission, in its
Radiological Protection Series, published a booklet with guidelines on education and trainingof medical professionals in radiological protection (EC, 2014b). This document is inagreement with Publication 113, and in fact reinforces its orientations, also defining: 1)
different categories or groups of health professionals, with corresponding levels ofknowledge and expertise expected; 2) objectives and topics for the education, training and
CPD; 3) orientations for credentialing entities for education in radiological protection.
(526) Both these two documents - Publication 113 (ICRP, 2009) and RadiologicalProtection N. 175 (EC, 2014b) - complement each other, and provide detailed contents foreducation and training in radiological protection for the different categories of healthprofessionals, including those not working directly with radiological procedures but referringto them, such as physicians from almost all medical specialities. They both also emphasisethat this education should start at undergraduate level, at medical and other health131

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4896
4897
4898
4899
4900
4901
4902
4903
4904
4905
4906
4907
4908

professional schools. Thus, they can both be the beacon that helps governments andresponsible entities to define frameworks and curricula for training and education inradiological protection and safety. Considering that these documents also include operational
topics in hybrid techniques, they can certainly help in assuring radiological protection andsafety in the performance of PET/CT or PET/MRI procedures.
(527) Also, two other international organisations can help in the development andcontinuing implementation of educational programs in radiological protection and safety,
working together with ICRP, IAEA, WHO and EC, namely, the European Training and
Education in Radiological Protection (EUTERP) Foundation and the Heads of the European
Radiological Protection Competent Authorities (HERCA), the first providing different
helpful training materials - available at its website - and the latter defining the criteria toobtain the highest levels of qualification in radiological protection and safety (HERCA,
2017).

4909

10.3. Main responsibilities regarding education and training

4910

10.3.1. Regulatory responsibilities

4911
4912
4913
4914
4915
4916
4917
4918
4919
4920
4921
4922
4923
4924
4925
4926
4927
4928
4929
4930
4931
4932
4933
4934
4935
4936
4937
4938
4939
4940
4941

(528) Publication 113 discusses the importance of a sound infrastructure for radiologicalprotection which begins with a government and the associated regulatory body setting aframework for the educational requirements for a country’s national strategy (ICRP, 2009).
This infrastructure will contribute to strengthening radiological protection and safety in
PET/CT.
(529) One of the most accepted and adopted international radiological protection standard
is the Radiation Protection and Safety of Radiation Sources: International Basic Safety
Standards. General Safety Requirements (No. GSR Part 3) (BSS), which describes important
standards for safety which should be implemented to ensure the safe use of medical imaging
using ionising radiation. It includes standards for education applied to professionals that work
delivering ionising radiation for medical uses, such as those in field of radiology or nuclear
medicine, and also states the need for an educational qualification required for all personnel
that are completing training (IAEA, 2014b).
(530) The BSS describes the responsibilities for these requirements starting with thegovernment, regulatory agencies and the institution responsibilities with specified training
criteria for speciality areas: 'The government is also responsible for ensuring, as necessary,that provision is made for support services, such as education and training, and technicalservices' (IAEA, 2014b). Each country will have its own laws and regulations relating toradiological protection including requirements for education, training, and competencies for
all professionals working with radiation and medical exposure (IAEA, 2014b).
(531) Many International Authorities cooperated with IAEA for the making of thisdocument, such as the WHO and the EC. The latter, through its Council Directive
2013/59/EURATOM and reinforcing previous Directives, continued imposing to all state
members the development of a legal frame for specialised education and training inradiological protection, and with particular considerations for the medical uses of ionisingradiation (Council of the European Union, 2013). Within this area, this European Regulatory
Body, in accordance with ICRP, reinforces the need to 'ensure continuing education andtraining after qualification is provided and, in the special case of the clinical use of newtechniques, training is provided on these techniques and the relevant radiological protection
requirements' as well as encourages 'the introduction of a course on radiological protection in
the basic curriculum of medical and dental schools' (Council of the European Union, 2013).
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4942
4943
4944
4945
4946
4947
4948
4949
4950
4951
4952
4953
4954
4955
4956
4957
4958
4959
4960
4961
4962
4963
4964
4965

(532) The BSS states that 'Competence of persons is normally assessed by the member
state by having a formal mechanism for registration, accreditation or certification of medical
radiation technologists in the various specialities (e.g. diagnostic radiology, radiation therapy,
nuclear medicine)' (IAEA, 2014b). In most countries national regulatory authorities either
provide the certification process or delegate it to a professional organisation in place of them.
This process happens for all these three professional categories of the medical imaging teamof the PET/CT or PET/MRI facility.
(533) The BSS also describes, that 'the regulatory body is responsible for carrying out its
required regulatory functions, such as the establishment of requirements and guidelines, theauthorization and inspection of facilities and activities, and the enforcement of legislative andregulatory provisions' (IAEA, 2014b). Most countries have established accreditation
standards relating to education and training for all medical staff. Inspections are mandated toensure these regulatory requirements were being met.
(534) Finally, the BSS states that 'the government shall ensure that requirements are
established for: (a) Education, training, qualification and competence in protection and safetyof persons engaged in activities relevant to protection and safety; (b) The formal recognitionof qualified experts; (c) The competence of organisations that have responsibilities relating toprotection and safety' (IAEA, 2014b).
(535) These rules ensure that governments have to establish provision in place to provide
the education, training and certification necessary to maintain the competency for all
professionals working in health with ionising radiation, and thus in a PET/CT or PET/MRI
department, ensuring that the facility or organisation takes on the responsibility to haveestablished policies and procedures that ensure this happens, with the safeguard of protection
and safety measures (IAEA, 2014b).

4966

10.3.2. Institutional responsibility

4967
4968
4969
4970
4971
4972
4973
4974
4975
4976
4977
4978
4979

(536) The BSS explains that not only governments, but also the facility or institution needs
to ensure that all personal have responsibilities in relation to protection and safety (IAEA,
2014b). Additionally, the facility or institution needs to provide appropriate education,
training and qualification. The BSS states ‘This process will ensure that all personnel will
have competency to perform their role with a full understanding and can perform their duties
with appropriate judgment and in accordance with procedures’ (IAEA, 2014b).
(537) In accordance with these orientations for this topic, the facility or institution has not
only to guarantee, before employing someone to work in the PET/CT or PET/MRI unit, thatthe worker has had the necessary education and training, certified by the applicable
Regulator, but also that each time a new technology or procedure is introduced, adequate
training is provided, as well as the employer has had CPD activities in topics related withradiological protection and safety, specific and appropriate for the installation of PET/CT or
PET/MRI.

4980

10.3.3. Health professional responsibility

4981
4982
4983
4984
4985
4986
4987

(538) Finally, each and every health professional that works with ionising radiation,
namely in a PET/CT or PET/MRI facility, has the responsibility to be committed to keep
themselves updated in their education and training in radiological protection and safety, as
well in the specific diagnostic modalities with which they work, in order to guarantee a safe
environment for patients, workers and public in general (IAEA, 2018). They also have to beavailable to work with their own organisations and authorities, in order to contribute to a
general culture of radiation safety and constructive uses of ionising radiation.
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4989

10.4. Health care professional training in radiological protection andsafety

4990
4991
4992
4993
4994
4995
4996
4997
4998
4999
5000
5001
5002
5003

(539) The education and training of the multidisciplinary team engaged in PET/CT or
PET/MR practices will depend on each of professional’s separate responsibilities. Included in
the training will be aspects of the radiation dose due to medical examination, the type oftechnological advancement in that area of practice, the type of equipment being operated andthe type of procedures being performed. Each health professional’s education and training
will incorporate a framework to ensure that the professional is academically prepared andclinically competent to work in their appropriate area of practice. PET/CT and PET/MR are
advancing technologies with emerging software, hardware and new radiopharmaceuticals
being frequently developed and introduced as standard patient imaging procedures that makeradiological protection an essential part of all educational training programs, which needfrequent updates. Publication 113 provides definitions for all personnel working in PET/CTor other medical areas with ionising radiation. This document also provides appropriate
formal educational categories for training as well as CPD categories for retraining for all
personnel working in PET/CT (ICRP, 2009).

5004

10.4.1. Nuclear medicine physician

5005
5006
5007
5008
5009
5010
5011

(540) Publication 113 defines different categories for physicians, according to their main
speciality or clinical field. According to this publication, the physicians that will be working
and reading the procedures that are produced in the PET/CT facility fall under Category 2
which defines them as 'nuclear medicine specialists: physicians who are going to take up a
career in which the major component involves the use of radiopharmaceuticals in nuclear
medicine for diagnosis and treatment including PET or PET/CT'. Their recommended
requirements in terms of radiological protection are defined in Table 10.1. (ICRP, 2009).

5012

10.4.2. Medical physicist

5013
5014
5015
5016
5017
5018
5019
5020
5021
5022

(541) Publication 113 defines Medical Physicists as a Category 9, medical physicist'specializing in radiological protection (RP), nuclear medicine, or diagnostic radiology'(ICRP, 2009). A medical physicist should have the highest level of training in radiologicalprotection and, in many countries, is the one that, at institutional and facility level, will beoverseeing the radiological protection program as a Radiation Safety Officer, including
teaching all medical staff in matters relating to radiological protection. A medical physicist
will also undertake the equipment acceptance testing, and annual or periodic QC, as well asadvise on optimisation of the dose for different protocols, working together with theremainder of the imaging team. Their recommended requirements in terms of radiologicalprotection are defined in Table 10.1 (ICRP, 2009).

5023

10.4.3. Nuclear medicine technologist/radiographer

5024
5025
5026
5027
5028
5029
5030

(542) Publication 113 defines a nuclear medicine technologist as a Category 10,'individual who is going to take up a career in which a major component of their work is
involved with operating and/or testing x-ray units, including those carrying out some tests on
a range of x-ray units in different hospitals and operating radionuclide imaging equipment'.
Their recommended requirements in terms of radiological protection are defined in Table
10.1 (ICRP, 2009).

4988

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Table 10.1. Recommended radiological protection training requirements for different categories of
personnel (ICRP, 2009).
Category
Training area
2 NM
9 MP
10 RDNM 13 NU
16 RL
Atomic structure, x-ray production, and
H
H
M
L
M
interaction of radiation
Nuclear structure and radioactivity
H
H
M
M
Radiological quantities and units
H
H
M
L
M
Physical characteristics of x-ray machines L
H
HL
Fundamentals of radiation detection
H
H
H
L
M
Principle and process of justification
H
H
H
L
Fundamentals of radiobiology, biological H
H
M
L
M
effects of radiation
Risks of cancer and hereditary disease
H
H
H
L
M
Risk of deterministic effects
H
H
H
L
L
General principles of RP including
H
H
H
M
M
optimisation
Operational RP
H
H
H
M
H
Particular patient RP aspects
H
H
H
M
Particular staff RP aspects
H
H
H
M
H
Typical doses from diagnostic procedures H
H
H
Risks from fetal exposure
H
H
H
L
M
Quality control and quality assurance
H
H
H
L
National regulations and international
M
H
M
L
M
standards
Suggested number of training hours
30–50
150–200 100–140
8–12
20–40

5033
5034
5035
5036
5037
5038
5039

L, low level of knowledge indicating a general awareness and understanding of principles; M, medium level ofknowledge indicating a basic understanding of the topic, sufficient to influence practices undertaken; H, highlevel of detailed knowledge and understanding, sufficient to be able to educate others.
NM, nuclear medicine specialists; MP, medical physicists specialising in RP, nuclear medicine, and diagnostic
radiology; RDNM, radiographers, nuclear medicine technologists, and x-ray technologists; NU, nurses assistingin x-ray or nuclear medicine procedures; RL, radiopharmacists and radionuclide laboratory staff.

5040

10.4.4. Nurses or other health care professionals

5041
5042
5043
5044
5045
5046
5047

(543) Publication 113, defines a Nurse and other health care professionals as a Category
13, 'individuals assisting in diagnostic and interventional x-ray fluoroscopy procedures,radiopharmaceutical administration, or the care of nuclear medicine patients'. Their
recommended requirements in terms of radiological protection are defined in Table 10.1.
(ICRP, 2009). Nurses and other health care professional assist during procedures (i.e.
Venepuncture, continuous Bladder irrigation or Sedation) in the PET/CT or PET/MR
department.

5048

10.4.5. Other professionals with a close relation with a PET/CT unit

5049
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5055

(544) Among other categories of professionals defined in Publication 113, two have not to
be forgotten in terms of radiological protection and safety, when considering activity in a
PET/CT or PET/MR facility, namely: the medical referrers (Category 8) - 'physicians whorequest examinations and procedures involving ionising radiations, and medical students who
may refer for examinations in the future'; and radiopharmacists (Category 16) –'radiopharmacists and radionuclide laboratory staff: radiopharmacists and individuals who
use radionuclides for diagnostic purposes such as radioimmunoassay' . The recommended
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requirements in terms of radiological protection for this latter category are defined in Table
10.1 (ICRP, 2009).

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10.5. Formal and informal educational training priorities and certificationin PET/CT

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(545) The imaging team, including the nuclear medicine physician, medical physicist andnuclear medicine technologist/radiographer, working in the PET/CT or PET/MRI department,
should undertake formal didactic education and training in radiological protection. This
includes coursework in radiation physics, radiation biology, radiation dosimetry, radiation
safety and protection principles, radiochemistry, radiopharmacology, instrumentation andquality control, just to mention a few topics of the formal courses needed. Since in theseUnits, hybrid equipment will be used, it is mandatory that these courses also include
knowledge in PET and in CT, and dose reduction in both imaging modalities. For thoseworking with hybrid equipment such as PET/MRI, courses should include knowledge relating
to MRI safety as well.
(546) Also, in all diagnostic facilities, including PET/CT or PET/MRI units, informal
training has to be kept continuously, meaning unstructured training in workplaces, driven by
the professional’s interest in continuous improvement and under close supervision of moredifferentiated and experienced team members.
(547) Formal and informal, didactic and clinical education help form the foundation for
the traditional core knowledge needed to build the appropriate skills required to undertake
duties assigned during the work day as a nuclear medicine physician, a medical physicist or a
nuclear medicine technologist/radiographer. This type of education also ensures that thefoundation of knowledge is there to appropriately achieve occupational radiologicalprotection for all members of the imaging team.
(548) Bozidar describes Certification as a 'formal process by which an authorised bodyevaluates and recognises the knowledge and proficiency of an individual, which must satisfy
pre-determined requirements or criteria' (Bozidar, 2016). The article also describes that theperson taking the certification should have performed some formal education and clinicaltraining with the established qualification. Most countries have established a certification
process for all medical personnel involved in nuclear medicine. Countries are trying toaddress additional training and education in hybrid techniques, including PET/CT and
PET/MRI.

5088

10.5.1. Nuclear medicine physician

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(549) Nuclear medicine physicians meet stringent education training standards and, as
other medical specialties, they are duly certified in Nuclear Medicine Specialty (e.g. in somecountries by the Medical Boards within Medical National Associations, and in Canada andUK by Royal Colleges certifications and fellowships). This certification includes formal
didactic education in radiation physics, instrumentation, radiochemistry, radiopharmacology,
radiation dosimetry, radiation biology, radiation safety and protection and quality control.
Additionally, they are clinical trained in PET/CT or PET/MRI including understanding
technical performance and acquisition parameters, how to apply appropriate calculation of
dosages, clinical justification for the procedures, evaluation of images and correlation withother diagnostic modalities and interpretations. In some countries, and with a tendency to
expand, they need also to obtain recertification at definite time intervals, in order to guaranteethat they are updated in their field of knowledge. This may be considered a compliance to136

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CPD and also a safeguard, relevant for radiological protection and safety, since it guarantees
that stay abreast on developing technology.
(550) In different continents and countries, we find that the regulating entities that certify
nuclear medicine physicians and radiologists trained in nuclear medicine define that, to workand have privileges to practice PET/CT or PET/MRI, the physicians have to prove knowledge
in radiological protection.
(551) In USA, the American College of Radiology, in 2021, published a document entitled'ACR–ACNM–SNMMI–SPR practice parameter for performing FDG -PET/CT in oncology'(ACR, 2021). From this document, it is understood that if a physician is not Board certified
by one of the Specialties boards that require education and training in radiation topics – suchas Nuclear Medicine or PET/CT – and wants to practice PET/CT, then the candidate will
have to present 'evidence of CME in PET/CT and of ongoing interpretation of oncologic
PET/CT' (ACR, 2021).
(552) In most of the countries within the European Union, only Nuclear Medicine certified
medical specialists are allowed to practice PET/CT, and the Section of Nuclear
Medicine/European Board of Nuclear Medicine of the Union Européenne des Médecins
Spécialistes/European Union of Medical Specialists (UEMS/EBNM) periodically publishes
syllabus to help member states, through their medical boards, to define their specialization
programs. At the last update of these syllabus, it is again stated, like in the previous versions,that a future nuclear medicine specialist, besides having to be trained incorrelative/multimodality imaging methods, such as CT, has also to have education anddevelop expertise in physics; radiation physics; data acquisition and image processing
techniques, including SPECT/CT and PET/CT; radiobiology; justification and optimisation[as low as reasonably achievable (ALARA), and as low as reasonably practicable (ALARP)
concepts]; limitation of doses; and radiation hazards (UEMS, 2017).

5126

10.5.2. Nuclear medicine technologist/Radiographer

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(553) Certification by the appropriate certification body in the field of practice is essential
for the nuclear medicine technologist/radiographer operating the PET/CT or PET/MRI
scanner. Nuclear medicine technologists/radiographer performing duties in the field of
nuclear medicine and the subspecialty of PET/CT or PET/MRI require formal education andtraining from a post-secondary institution with academic courses to include radiology, healthsciences, patient care, nuclear medicine technology and radiological protection and safety.
Formal education and training from a post-secondary institution vary from country tocountry. The major of European countries combines initial radiographer education curriculumwith either nuclear medicine or radiotherapy education curriculum. Graduates in thesecountries are fully qualified to work in all of the areas of their combined programme. Rare is
the nuclear medicine only education curriculum in Europe. In the United States a postsecondary formal education and training is the standard with nuclear medicine being the
focus and additional education being provided in CT. With the advent of hybrid imaging suchas PET/CT or PET /MRI, additional education was developed to ensure the nuclear medicine
technologist /radiographer can cross train to operate the CT or MRI component. Just recently
MRI Safety was added to the formal education and curriculum in the United States.
(554) Once the nuclear medicine technologist/radiographer obtains a diploma from aformal education institution, most countries will mandate these professionals working in the
nuclear medicine field and the subspecialty of PET/CT or PET/MRI to take a mandatory
national certification exam. This national certification will demonstrate a mastery of the bodyof knowledge in the field of nuclear medicine and in some countries additionally a PET/CT

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or PET/MRI component. Some countries have developed an additional certification for the
CT component of the PET/CT or MRI component of PET/MRI.
(555) The passing of a national certification examination recognises that a nuclear
medicine technologist/radiographer is educationally prepared and clinically competent toperform procedures and routine tasks within the nuclear medicine scope of practice.
Additional informal training in the field of PET/CT or PET/MRI will prepare the nuclear
medicine technologist/radiographer with the base knowledge to perform procedures androutine tasks within the PET/CT or PET/MRI scope of practice.

5156

10.5.3. Medical physicist

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(556) The medical physicist should be highly qualified, trained and be board-certified in
an area of practice. Medical physicists attend in accredited college or university to attain theirformal graduation in the field of physics, engineering, medical physics or bioengineering and,additionally, in many countries, in order to practice in healthcare organisations, this iscomplemented with a residency period (e.g. 3 years program, in Spain) in a hospital, to obtaina certified speciality diploma as Medical Physicist, sometimes with subspecialties (e.g.
Nuclear Medicine, Radiology and Radiation Oncology). Once finished with the formal
training, the medical physicist may also go on to attend a master's or doctoral degree inphysics, medical physics, biophysics, radiological physics, or medical health physics tocomplete their formal education process.
(557) Some physicists gain a certification in a subfield of medical physics with a national
certifying body, which demonstrates a mastery of that body of knowledge. The passing of thenational certification exam demonstrates that the medical physicist is educationally preparedand clinically competent to work in the medical physics subspecialty area of practice and canperform routine tasks within that scope of practice which in this instance would be nuclear
medicine, PET and/or CT or MRI.
(558) Some scientific organisations contribute to homogenise and define standards for thiscertification in Medical Physics, such as the European Federation of Organisations for
Medical Physics (EFOMP), who together with EANM in 2013 published a curriculum foreducation and training of medical physicists in nuclear medicine (Del Guerra et al., 2013),
and in 2017 published a Policy Statement concerning Medical Physics Education andTraining (EFOMP, 2017).
(559) Professional certification of medical physicists is established either by a government
body within a country or by a national medical physics organisation authorised by thegovernment. The medical physicist, then follow a formal registration, which is generally
operated at the national level by an official authority (e.g. Ministries of Health) or
professional medical physics society/organisation authorised by the government. Also, these
professionals, in some countries, to act as Radiation Protection Safety Officer within afacility, such as a PET/CT or PET/MRI unit, need to have a separate certification as
Radiation Protection Experts, and with different degrees of responsibility and knowledge. For
instance, in the European Community, the Council Directory 2013/59/EURATOM obliges
member states to 'establish the arrangements for the recognition of radiological protection
experts', as a separate recognition from the one of medical physicist, although these
professionals may have double certification. (Council of the European Union, 2013).
(560) In Europe, after the publication of Council Directive 2013/59/EURATOM, EFOMP
also provided some guidelines to help National Regulatory Bodies to organise the structure
for medical physicist’s registry. In 2016, EFOMP also published a Policy Statement withguidelines for National Registration Schemes applicable to Medical Physicists (Christofides
et al., 2016).
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5196

10.5.4. Nurses working in nuclear medicine facilities

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(561) Registered nurses that work in nuclear medicine, including PET/CT or PET/MRI
facilities, need to have special training not only in radiological protection but also in the
nuclear medicine procedures in which they cooperate, with a particular emphasis in the safe
handling of radiopharmaceuticals.
(562) In most countries, worldwide, there is not a nurse’s specialisation in nuclear
medicine, as there is in other clinical areas, such as oncology, for example. So, most of the
training in nuclear medicine for nurses is informal, in the workplace, supervised by the otherdedicated staff with certification in nuclear medicine, such as physicians and technologists.
Some guidelines for this training-in-service are provided by some scientific organisations in
nuclear medicine (BNMS, 2010).
(563) Nevertheless, to be allowed to work in nuclear medicine, most National Regulatory
Bodies define as mandatory that they receive training in radiological protection and safety bya certified organism for education, or, when this is not the case, by a medical physics expert
or the Radiation Protection Officer of the facility. To define the curricula for theseeducational programs, guidelines are provided either in Publication 113 (ICRP, 2009) or in
Radiation Protection N. 175 (EC, 2014b).

5213

10.5.5. Radiopharmacists and radionuclide laboratory staff

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(564) In radiopharmacies or nuclear medicine laboratories, materials andradiopharmaceuticals can be prepared by nuclear medicine technologists/radiographers, butalso by pharmacists or other clinical scientists, that had specialised training in radiopharmacy.
In some countries, it is compulsory that radiopharmacy activity be performed under thesupervision of a certified radiopharmacist.
(565) Qualification as radiopharmacist, depending on National legal requirements, can beachieved either by a residency program, similar to the one organised for physicians or
medical physicists; or by a postgraduation program at university.
(566) These qualification programs include topics in radiological protection and safety, forwhich contents guidelines are provided in Publication 113 (ICRP, 2009).

5224
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10.6. Continuous professional development (CPD) and self-assessment
needs

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(567) Most professions in the medical field mandate CPD education and continuous
learning. A common definition for this is a structured approach to learning to help ensurecompetence to practice, taking into account knowledge, skills and practical experience. There
are many educational tools that can be accessed to obtain CPD with some being formal andstructured, and others more informal being self-directed based on individual needs. They
should however, meet requirements of the body overseeing the award of CPD accreditation.
Advancing technologies and changes to the standard of care for patients require additional
knowledge and skills to sustain the expertise and knowledge needed to ensure optimal
radiological protection of the medical dose and safe practice in the medical field for all
professionals in the PET/CT or PET/MRI department.

5236

10.6.1. Nuclear medicine physician continuing education

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(568) Physicians continue their medical education with lifelong learning, which starts withthe physician being licensed to practice in their country and get a board certification in adefinite speciality like Nuclear Medicine, after which, in some countries, the medical
physician will be subject to recertification, using proof of their lifelong learning records
through the accredited medical education programs. Depending on the physician speciality acertain number of hours of specific medical education will be required relating specifically totheir medical practice. Some credit is given relating to that of a general nature. A second partof physician’s continuous education is a cognitive assessment were physician complete selfassessment modules during a predetermined time frame. Finally, physicians also have tocomplete a practice performance assessment and if necessary, an improvement project thatmeet the countries requirements.
(569) The presence and practice of a physician with a recognised specialization in nuclear
medicine, which includes expertise in PET/CT or PET/MRI, is a legal requirement to keep
the clinical activity in the facility. Due to the exponential growth of knowledge in this field of
medical practice, it is also compulsory that these nuclear medicine physicians keep and haveevidence of CPD with certified programs, in many countries indispensable to guarantee thecompulsory recertification process. Nowadays, many National and International Societies,
such as the SNMMI and the EANM, provide high level and certified CPD modules, in all
fields, including radiological protection and safety topics in PET/CT or PET/MRI, such as
clinical justification, dosimetry, dose reduction and optimisation and MRI safety.

5257

10.6.2. Nuclear medicine technologist/radiographer continuing education

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(570) As the field of Nuclear Medicine, PET/CT and PET/MRI is continually changing
there is a need for professionals working together to continue to accumulate knowledge intheir field of practice. CPD or continuing education courses are typical platforms, that uses
educational tools for nuclear medicine technologists/radiographers to engage and demonstrate
a continued accumulation of knowledge in the field of practice. It is a way to ensure that thenuclear medicine technologist/radiographer is educationally prepared and clinicallycompetent in their area of practice.
(571) Safe operation of the equipment and safe operation of procedures requires some typeof formal and informal education with an assessment tool to demonstrate competency before
undertaking medical procedures on patients using the PET/CT or PET/MRI equipment. Thus,
CPD is a key component in contributing to the quality of professional practice, including
updated education in optimisation of radiological protection, radiation safety, theunderstanding of radiation effects, MRI safety, the role of quality management including
quality assurance and quality control.
(572) National and International scientific and professional organisations, such as theInternational Society of Radiographers and Radiological Technologists (ISRRT), the SNMMI
and the EANM offer a variety of educational material including CPD, online PET Review
workshop and educational review programs, which are designed to help contribute to theprofessional knowledge in the field of practice as well as prepare nuclear medicine
technologist/radiographer to take advanced certification board in PET/CT or PET/MRI.

5278

10.6.3. Medical physicist continuous professional development

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(573) Medical Physicists need to engage in CPD or continuing education in the basic
physics concepts, basic medical topics, instructions for performing procedures and emerging
technologies.

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(574) Again, many national and international scientific and professional organisations,such as Institute of Physics and Engineering in Medicine (IPEM) and EFOMP, provide highlevel educational modules, that help medical physicists to keep updated in their fields ofexpertise, and thus relevant for PET/CT or PET/MRI instrumentation and operational
radiological protection.
(575) EFMOP provides CPD-activities e.g., through an e-learning platform, summer
schools, and refresher courses at the biannual congress ECMP. They also offer a European
Diploma in Medical Physics, which can be considered a CPD activity, since it is notcompulsory to undertake medical physics professional activity in the European Community.

5291

10.6.4. Nurses continuous professional development

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(576) Nurses working in nuclear medicine departments, including PET/CT or PET/MRI
facilities, are subject to the conditions for recertification or continuous professional
development applied in their own countries, related to their job descriptions and functional
content of their profession as nurses.
(577) Regarding the specific activity in nuclear medicine and topics in radiologicalprotection and safety, they also attend educational and scientific modules provided by thenational and international societies in the field.

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10.6.5. Radiopharmacists and radionuclide laboratory staff continuing education

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(578) For these groups of professionals, the situation is the same as the nurses, i.e. they
have to comply to national requirements in terms of recertification or continuous professional
development, related to their specific profession; but they also have available different
educational and scientific programs provided by scientific societies, such as SNMMI and
EANM.
(579) EANM, in collaboration with the Swiss Technical University, provides also a
Postgraduate Certificate Course in Radiopharmaceutical Chemistry/Radiopharmacy, valid for
5 years, and with compulsory modules in PET radiopharmaceuticals. This can also be
considered a CDP activity, since the Certificate obtained is not compulsory to practise
radiopharmacy in the European Community.

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10.6.6. ICRP recommendations for continuous profession development education for all
medical staff in PET/CT

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(580) Publication 113, outlines contents for CPD education which can be used to define
courses to guarantee that nuclear medicine physicians, nuclear medicine
technologists/radiographers and medical physicists, stay current in all topics relevant to both
Operational Radiological Protection and Optimisation of medical dose. These comprehensive
lists of topics include education regarding optimisation of radiological protection for
professionals that administer radiopharmaceutical to patients, operation of PET/CT
equipment, performance of quality control, interpretation of images to ensure radiologicalprotection and radiation safety including additional requirements as listed below' (ICRP,
2009):(581) Regarding nuclear medicine physicians and technologists (Categories 2 and 10, as
defined in Table 10.1), Publication 113, in the subheading A.1. of its ‘Annex A. Examples ofsuggested content for training courses’ provides detailed orientation to prepare course
materials relevant for the practice of PET/CT (ICRP, 2009).

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(582) Topics related to education in the CT component of the PET/CT studies, can also befound in the ‘Annex B. Outline of specific educational objectives for Paediatric Radiology’ of
Publication 113 (ICRP, 2009).
(583) Finally, Publication 113 provides examples of sources of training material in its
Annex C (ICRP, 2009).

5330

10.7. Final remarks

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(584) Expertise in PET/CT or PET/MRI, as any other modality of work with ionisingradiation or magnetic radio waves, includes being highly knowledgeable in radiologicalprotection, in order to guarantee a positive benefit-risk ratio and a safe environment both forpatients, workers and public in general.
(585) Education and training in radiological protection and safety, has to guarantee
expertise in these fields, at the level of practice of each health professional, and has to berobust, evidence-based, and accredited by authorities in the field.
(586) The present section tried to revise guidance provided by international authorities andmain stakeholders in this field of knowledge, in order to help identify what cannot be missedby any healthcare professional working in PET/CT or PET/MRI, in terms of education(undergraduate and postgraduate), training and continuous progressive development in topics
relevant for radiological protection and safety.

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DRAFT REPORT FOR CONSULTATION: DO NOT REFERENCEACKNOWLEDGEMENTS

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This publication is the result of Task Group 117 on Radiological Protection in PET and
PET/CT established by the Commission, during the annual meeting held in Adelaide,
Australia on 15–17 November 2019. A Working Party of ICRP Committee 3 was createdduring the annual committee 3 meeting held in Beijing, China, on 8–11 November 2018 toinvestigate the needs of the medical radiological protection community.

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J.M. Martí-Climent (Chair)S. Demeter

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J.M. Martí-Climent (Chair)S. Demeter
S. Holm
M. Hosono

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Task Group 117 technical secretary

ICRP thanks all those involved in the development of this publication for their hard work anddedication, and members of Committee 3 for their helpful comments on draft report. Thankyou to internal C3 discussion, reviews and valuable comments.
The membership of the Working Party was as follows:
K. Kang
M. Hosono

K. Kang
M. Marengo
C. J. Martin

C. J. Martin

D. Newman
A. I. Santos
F. Vanhavere

F. Eze6236

Committee 3 critical reviewers

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M.-C. Cantone

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Main commission critical reviewers

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K.W. Cho
D.A. Cool

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Editorial members

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C.H. Clement (Scientific Secretary and Annals of the ICRP Editor-in-Chief)
T. Yasumune (Assistant Scientific Secretary and Annals of the ICRP Associate Editor)
H. Yu (Assistant Scientific Secretary and Annals of the ICRP Associate Editor)

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Committee 3 members during preparation of this publication

6246(2017–2021)

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K. Applegate (Chair)
C.J. Martin (Vice-Chair)

M. Mahesh

M. KaiJ. C. Paeng

E. Vañó

S. Demeter
M. Hosono
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C. Ruebe
W. Small

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M. Rehani (Secretary)
J. Alsuwaidi
M. Bourguignon
M.C. Cantone

K. Kang
R. Loose
J.M. Martí-Climent
Y. NiuD. G. Sutton
L. Van Bladel

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K. Applegate (Chair)
C.J. Martin (Vice-Chair)
D.G. Sutton (Secretary)
M.C. Cantone
J. Damilakis
M. Hosono

A. Isambert
M. Kortesniemi
M. Mahesh
J. M. Martí-Climent
J.C. Paeng
C. Ruebe

W. SmallÅ. Søvik
I. Thierry-Chef
I. Williams
W. Zhuo

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S. Mattsson

M.M. Rehani

M. Rosenstein

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Chair: C.W. Rühm, Germany
Vice-Chair: D. Cool, USA
Scientific Secretary: C.H. Clement, Canada; sci.sec@icrp.org *(2021–present)

Committee 3 emeritus members

Main Commission members at the time of approval of this publication

K. Applegate, USA
F. Bochud, Switzerland
S. Bouffler, UK
K.W. Cho, Korea
G Hirth, Australia
M. Kai, Japan

D. Laurier, France
S. Liu, China
S. Romanov, Russia
T Schneider, France
A Wojcik, Sweden

Emeritus Members
R.H. Clarke, UK
F.A. Mettler Jr., USA
R.J. Pentreath, UK
R.J. Preston, USA
C. Streffer, Germany
E. Vaño, Spain* Although formally not a member since 1988, the Scientific Secretary is an integral part of
the Main Commission
Finally, thank you very much to all organisations and individuals who took the time toprovide comments on the draft of this publication during the consultation process.

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